Climate Variables

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. It is especially important to know how our winters will change in the future, because cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Cooling Degree Days are often used to estimate how much air-conditioning is required in a year. If a location shows an increase in projected CDD values, this implies that it will experience hotter or longer summers.

18 °C is the temperature at which air conditioning is required to maintain a comfortable temperature inside buildings. A place that gets many days with average temperatures above 18 °C or that gets mean temperatures much higher than 18 °C will require a relatively large amount of energy (and thus money) to cool buildings for comfort and safety.

One of the common climate indices used to assess the viability of growing a crop in a region is average annual CHUs. The CHUs expected in a region’s growing season are used to assess whether corn, or a particular variety of corn, is likely to fully mature in that region. Very generally, at least 2200 CHUs are required to mature most varieties of corn.

Note that this index is only based on temperature and does not take into account the availability of water to grow the crop.

The arrival of frost marks the end of the growing season and announces the imminent return of winter. If projections show a later Date of First Fall Frost, then the seasonal transition from warmer to colder weather is happening later in the year.

Changes in the length and timing of the frost-free season affect plant and animal life, but also our social, psychological, and physical experience of the changing seasons.

The growth of most plants and crops is limited by the temperature of the air and soil. Since crops and plants need time to mature, the later in the fall they experience freezing temperatures, the more likely it is that they will be able to mature to their full potential. Of course, the time available for growth, maturity and productivity of these plants is also determined by the Date of Last Spring Frost that, together with the Date of First Fall Frost, determines the overall length of the frost-free season.

The final frost in the early spring marks the beginning of the growing season and announces the imminent return of summer. If projections show an earlier Date of Last Spring Frost, then the transition from colder to warmer weather is happening earlier in the year.

Changes in the length and timing of the frost-free season affect plant and animal life, but also our social, psychological, and physical experience of the changing seasons.

For most crops and plants, emergence and growth in the spring is limited by freezing temperatures in the air and soil. Since crops and plants need time to mature, the earlier in the spring they start to grow without the occurrence of frost, the more likely it is that they will grow to their full potential. Of course, the time available for growth, maturity and productivity of these plants is also determined by the Date of First Fall Frost that, together with the Date of Last Spring Frost, determines the overall length of the frost-free season.

Precipitation patterns are critical for many important issues, including water availability, crop production, electricity generation, wildfire suppression, snow accumulation, seasonal and flash-flooding, and short- and long-term drought risk.

Locations that experience precipitation frequently, such as along coasts, have a low number of Dry Days, whereas locations that experience precipitation infrequently have a high number of Dry Days.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

Freeze-thaw cycles can have major impacts on infrastructure. Water expands when it freezes, so the freezing, melting and re-freezing of water can over time cause significant damage to roadways, sidewalks, and other outdoor structures. Potholes that form during the spring, or during mid-winter melts, are good examples of the damage caused by this process.

High FDD values are associated with relatively cold conditions: places with high FDD values likely get many days with temperatures significantly below freezing. If projections show a decrease in FDDs, then that location is likely to experience shorter or less severe winters.

High FDD likely imply greater snow and ice accumulation, which is an important consideration for winter activities such as skiing, the building of winter roads, municipal and rural snow clearance, and many other aspects of winter life. Such places would likely require a relatively large amount of energy for heating.

The number of frost days is an indicator of the length and severity of the winter season. A location with a large number of frost days is also likely to have a short growing season, since frost is harmful to many plants.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. It is especially important to know how our winters will change in the future, because cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Changes in the length and timing of the Frost-Free Season affect plant and animal life, but also our social, psychological, and physical experience of the changing seasons.

The average length of the growing season (and its year-to-year variability) is an important consideration when selecting or predicting what plants might grow well in a region. A longer Frost-Free Season means plants and crops have a longer window to grow and mature.

If projections show an increase in the length of the Frost-Free Season, then the annual growing season will be longer, and the period of cold weather correspondingly shorter.

Growing Degree Days (GDDs) are often used to determine whether a climate is warm enough to support plants and insects with temperature-dependent growth rates.

GDDs accumulate whenever the daily mean temperature is above a specified threshold temperature. Generally, 5 °C GDDs are used for assessing the growth of canola and forage crops; 10 °C GDDs are more appropriate for assessing the growth of corn and beans; and 15 °C GDDs are used to assess the growth and development of insects and pests.

Growing Degree Days (GDDs) are often used to determine whether a climate is warm enough to support plants and insects with temperature-dependent growth rates.

GDDs accumulate whenever the daily mean temperature is above a specified threshold temperature. Generally, 5 °C GDDs are used for assessing the growth of canola and forage crops; 10 °C GDDs are more appropriate for assessing the growth of corn and beans; and 15 °C GDDs are used to assess the growth and development of insects and pests.

Growing Degree Days (GDDs) are often used to determine whether a climate is warm enough to support plants and insects with temperature-dependent growth rates.

GDDs accumulate whenever the daily mean temperature is above a specified threshold temperature. Generally, 4 or 5 °C GDDs are used for assessing the growth of canola and forage crops; 10 °C GDDs are more appropriate for assessing the growth of corn and beans; and 15 °C GDDs are used to assess the growth and development of insects and pests.

Growing Degree Days (GDDs) are often used to determine whether a climate is warm enough to support plants and insects with temperature-dependent growth rates.

GDDs accumulate whenever the daily mean temperature is above a specified threshold temperature. Generally, 5 °C GDDs are used for assessing the growth of canola and forage crops; 10 °C GDDs are more appropriate for assessing the growth of corn and beans; and 15 °C GDDs are used to assess the growth and development of insects and pests.

Heating Degree Days are a measure of how much heating is required in a year. 18 °C is the temperature below which heating is required to maintain a comfortable temperature inside buildings. A place that gets many days with average temperatures below 18 °C or that gets mean temperatures much below 18 °C will require a relatively large amount of energy (and thus money) to heat buildings for comfort and safety.

If a location shows a decrease in projected HDD values, this implies that it will experience shorter periods of cold weather, or that it will experience less severe cold.

What counts as a Heavy Precipitation Day (HPD) depends on where you live: some places in Canada rarely get 10 mm of rain in a day, whereas others often do. The Climate Atlas offers two versions of HPD: days on which either 10 mm or 20 mm or more of rain (or its frozen equivalent, usually snow) falls.

Heavy rainfall events can create many challenges. In cities and towns, heavy rainfalls can overwhelm storm drains and cause flash flooding. They can also cause problems in rural areas by drowning crops, eroding topsoil, and damaging roads.

Heavy snowfall events can disrupt ground transportation, and very heavy snowfall events can cause damage to buildings if their roofs become overburdened.

What counts as a Heavy Precipitation Day (HPD) depends on where you live: some places in Canada rarely get 10 mm of rain in a day, whereas others often do. The Climate Atlas offers two versions of HPD: days on which either 10 mm or 20 mm or more of rain (or its frozen equivalent, usually snow) falls.

Heavy rainfall events can create many challenges. In cities and towns, heavy rainfalls can overwhelm storm drains and cause flash flooding. They can also cause problems in rural areas by drowning crops, eroding topsoil, and damaging roads.

Heavy snowfall events can disrupt ground transportation, and very heavy snowfall events can cause damage to buildings if their roofs become overburdened.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

The number of days on which the air temperature does not rise above freezing is a good indicator of the length and severity of the winter season.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. It is especially important to know how our winters will change in the future, because cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

This value indicates the most precipitation that falls in a single day, and is sometimes also called the “wettest day of the year”. This amount could be the result of a short but intense precipitation event such as a storm or because a moderate amount of snow/rain falls continuously all day, rather than all at once.

Very high precipitation totals and/or very high precipitation rates create many challenges. In cities and towns, high precipitation rates overwhelm storm drains and cause flash flooding. They can also cause problems in rural areas by drowning crops, eroding topsoil, and damaging roads.

Heavy snowfall events can disrupt ground transportation, and very heavy snowfall events can cause damage to buildings if their roofs become overburdened.

In regions where snow and/or rain tends to fall for multiple days in a row, the Max 3-Day Precipitation total may be a better metric of the total volume of precipitation a region should expect to receive at one time than the 1-Day Precipitation total.

Very high precipitation totals and/or very high precipitation rates create many challenges. In cities and towns, high precipitation rates overwhelm storm drains and cause flash flooding. They can also cause problems in rural areas by drowning crops, eroding topsoil, and damaging roads.

Heavy snowfall events can disrupt ground transportation, and very heavy snowfall events can cause damage to buildings if their roofs become overburdened.

In regions where snow and/or rain tends to fall for multiple days in a row, the Max 5-Day Precipitation total may be a better metric of the total volume of precipitation a region should expect to receive at one time than the 1-Day Precipitation total.

Very high precipitation totals and/or very high precipitation rates create many challenges. In cities and towns, high precipitation rates overwhelm storm drains and cause flash flooding. They can also cause problems in rural areas by drowning crops, eroding topsoil, and damaging roads.

Heavy snowfall events can disrupt ground transportation, and very heavy snowfall events can cause damage to buildings if their roofs become overburdened.

The temperature range we expect within a season or year is a very important aspect of climate. Changes in average and extreme temperatures can dramatically affect our everyday lives as well as a wide range of planning and policy decisions.

The average highest temperature is an environmental indicator with many applications in agriculture, engineering, health, energy management, recreation, and more. The maximum temperature is also used to compute a number of other maps and indices in this Atlas.

The temperature range we expect within a season or year is a very important aspect of climate. Changes in average and extreme temperatures can dramatically affect our everyday lives as well as a wide range of planning and policy decisions.

The average temperature is an environmental indicator with many applications in agriculture, engineering, health, energy management, recreation, and more. The average temperature is used to compute a number of other maps and indices in this Atlas.

Mild Winter Days indicate how much a location experiences moderately cold temperatures.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. It is especially important to know how our winters will change in the future, because cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Ski slope operators generally require temperatures below -5 °C to make artificial snow.

The temperature range we expect within a season or year is a very important aspect of climate. Changes in average and extreme temperatures can dramatically affect our everyday lives as well as a wide range of planning and policy decisions.

The average lowest temperature is an environmental indicator with many applications in agriculture, engineering, health, energy management, recreation, and more. The average temperature is used to compute a number of other maps and indices in this Atlas.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

Precipitation patterns are critical for many important issues, including water availability, crop production, electricity generation, wildfire suppression, snow accumulation, seasonal and flash-flooding, and short- and long-term drought risk.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

Hot summer days are physiologically stressful, especially if overnight temperatures do not provide cooling relief. Many people are at risk from suffering heat exhaustion or heat stroke when nighttime temperatures fail to drop below 20 °C. Elderly people, the homeless, and those who live in houses or apartments without air conditioning are especially vulnerable during these heat events, particularly if they last for more than a few days.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

Very cold days are an indicator of winter severity.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. It is especially important to know how our winters will change in the future, because cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Very Hot Days are an indicator of summer heat.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. It is useful to know how high summer temperatures are likely to become in the future, to make sure that our cooling and air-conditioning systems can reliably deal with these extremes.

When temperatures are very hot, people - especially the elderly - are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures. In general, Canadians are not used to extremely hot summers, and further warming will bring new and unusual risks as well as a very different experience of the summer season.

High, persistent temperatures increase the risk of drought, which can severely impact food production and increases the risk of wildfire. High temperatures can also lead to more thunderstorms, which means increased risks of flash flooding, lightning, hail and perhaps even tornadoes.

Precipitation patterns are critical for many important issues, including water availability, crop production, electricity generation, wildfire suppression, snow accumulation, seasonal and flash-flooding, and short- and long-term drought risk.

Locations that experience precipitation frequently, such as along coasts, have a high number of Wet Days, whereas locations that experience precipitation infrequently have a low number of Wet Days.

Winter Days are an indicator of how cold winters are. Few places in Canada never see -15 °C temperatures, making this index a good indicator of how winter cold is projected to change across the country.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. It is especially important to know how our winters will change in the future, because cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.