Introduction

Cold snaps—short periods of unusually cold weather—are a longstanding feature of Canadian winters. They can strain energy systems, disrupt transportation, and pose risks to health and safety, particularly for vulnerable populations. While cold snaps continue to occur, their character is changing in a warming climate. Observations across Canada show that cold extremes are becoming less severe, with minimum temperatures during cold snaps trending warmer over time.

This article examines how cold snaps are evolving in the context of climate change, explores current scientific understanding of the drivers behind these events, and highlights how tools available on ClimateData.ca can support planning and adaptation.

Cold snaps are changing, not disappearing

While cold snaps continue to occur, extreme cold temperatures in Canada have become less severe over time. Averaged across the country, the annual lowest daily minimum temperature* increased by more than 3 °C between 1948 and 2016, with the strongest warming in the west. This means that, in general, today’s coldest nights are warmer than in the past, even if they still feel extreme. Only about 0.5 °C of the  3 °C increase between 1948 and 2016 can be related to natural internal climate variability.  As much as 2.8 °C of the  3 °C increase can be attributed to human causes.  In most places in the world, it is virtually certain that there will be fewer cold temperature extremes as global average temperatures increase. This is the case for Canada.[4]

* Daily minimum temperature corresponds to the lowest temperature recorded in a 24-hour period. The majority of the daily minimum temperatures recorded in Canada occur during the night-time hours rather than during the daytime.

Researchers are working to understand the factors that shape cold snaps in a warming climate. Some studies point to changes in the tropics, where shifting ocean–atmosphere patterns can influence the jet stream — the high-altitude current of fast-moving air that helps steer weather systems. Other research points to the rapidly warming Arctic, where sea ice loss and rising surface temperatures may affect large-scale atmospheric circulation. These changes can disrupt the “polar vortex,” a band of strong winds that normally circles the Arctic high in the stratosphere and helps contain the coldest air. When the vortex weakens or becomes unstable, lobes of cold Arctic air can sometimes spill south into mid-latitudes.

While these processes have the potential to shape winter weather far from the Arctic, currently there is only low to medium confidence in the strength and consistency of these linkages. For example, while weak polar vortex events are becoming somewhat more common, studies do not show a corresponding increase in mid-latitude cold snaps. A study by Lee (2019) found that the North American weather regime, most closely tied to extreme cold, does not depend strongly on vortex strength, suggesting that weakened vortex events do not always lead to widespread cold extremes. Research to better understand these dynamics is ongoing.[5]

Warming, not increasing cold, is of greatest concern

Although cold snaps have impacts on our activities during their occurrence, the overall warming conditions in Canada are generally of more concern. Warming temperatures, particularly in winter in northern Canada, are resulting in the following impacts:[6]

• Decreases in the length of the snow cover season, with later onset in the fall and earlier spring melt.
• Replacement of perennial sea ice by thinner seasonal sea ice.
• Declines in the duration of seasonal lake ice cover, with earlier spring break-up and later freeze-up in the fall.
• Increases in permafrost temperatures and the thickness of the active layer.

These changes are impacting northern communities in particular – and projections indicate continued warming into the future. For example, warmer winters impact food security for many Indigenous and rural residents by disrupting access to hunting grounds and influencing species’ abundance and range (i.e., changing sea ice conditions). Shortened winter road seasons limit the time available to deliver supplies by land to remote communities. Thawing permafrost is causing damage to buildings and other infrastructure. Furthermore, loss of coastal sea ice has resulted in increased wave action and coastal erosion, which threatens some coastal communities.[7]

Information from ClimateData.ca

ClimateData.ca provides users with projections for several variables and indices that are related to cold snaps.

• Coldest Day – The Coldest Day describes the lowest nighttime temperature in the selected time period. In general, the coldest day of the year occurs during the winter months.
• Days with Tmin < -15 °C – Days with Tmin <-15 °C describes the number of days where the lowest temperature of the day is colder than -15 °C. This index gives an indication of the number of very cold days in the selected time period.
• Days with Tmin < -25 °C – Days with Tmin <-25 °C describes the number of days where the lowest temperature of the day is colder than -25 °C. This index gives an indication of the number of extreme cold days in the selected time period.
• Ice days – Ice Days describe the number of days where the warmest temperature of the day is not above 0 °C.

Analysis functionalities available on the Download page also allow users to calculate tailored indices (e.g., the number of cold spell days, and days with minimum temperature below specific threshold values) by using custom threshold values more suited to their location.

You can also read more about winter weather and climate change on ClimateData.ca:

• Map of the Month: Ice Days — ClimateData.ca
• Map of the Month: Days below -25 °C — ClimateData.ca
• Climate Data in Action: Outdoor skating rinks in Canada — ClimateData.ca

Conclusion

While cold snaps remain a familiar part of Canada’s winters, they are evolving due to climate change. Rather than becoming more frequent or intense, cold snaps are generally warming – a trend that reflects broader shifts driven by human-induced climate change. At the same time, changes in the Arctic and tropics may be altering winter circulation patterns in ways that add variability, creating the possibility of disruptive cold snaps when conditions align. Understanding the dynamics at play is crucial, and ClimateData.ca provides data and tools that can be utilized to inform ongoing adaptation efforts.

Further Reading

This blog is inspired by the “Quick Facts for Any Story” series developed by Susan Hassol in partnership with the American Association for the Advancement of Science’s SciLine project, with local context provided by ECCC’s Climate Research Division and Canada’s regional climate service providers.