Extreme cold

Climate change is generally expected to lead to warmer winters, while paradoxically, arctic warming is also leading to more extreme cold events. However, defining extreme cold is difficult in a place like Canada, which due to its vast landscape experiences a wide variety of local climates. In some regions, extreme cold alerts are issued for temperatures below -40°C, whereas in other regions, alerts are issued for -2°C or lower.  This discrepancy is ultimately a reflection of a region’s overall preparedness for cold, acclimatization of its residents, and wind chill effects.  In 2025, the Government of Canada’s approach to public weather alerts changed, introducing a new colour-coded system. Alongside this, weather impact guides set out the adverse impacts expected during a range of conditions, including extreme cold temperatures or wind chill. Jurisdictions may use these resources alongside local information.to inform decision making on alerts and response protocols.

The two major health risks of extreme cold are frost bite and hypothermia. While anyone can be at risk, some people are more at risk than others, including infants (<1 year), seniors (65+), and people consuming alcohol or nicotine among others. Contextual risk factors can also contribute to a person’s susceptibility to extreme cold; these include spending large portions of the day outdoors (i.e. outdoor workers and outdoor enthusiasts), experiencing homelessness or living in a home without adequate electricity or heat (also known as living in a state of energy or fuel poverty). Cold weather (both moderate and extreme) has also been linked to higher rates of  from several causes such as increased spread of infection, and mechanisms that lead to cardiovascular and respiratory events. These causes have been shown to have a delayed effect, occurring several days and up to several weeks after cold weather exposure. There are also indirect health impacts when individuals spend more time indoors that may thereby increase their exposure to indoor health hazards.

The resources listed below are intended to assist environmental public health professionals with the management of extreme cold events, including health and safety precautions to take during cold weather, and considerations for issuing extreme cold alerts.

Considerations for issuing extreme cold alerts

• Weather impact guides (Environment and Natural Resources Canada, 2025)
  This webpage sets out the weather impact guides that help set the criteria for the colour -coded weather alert system adopted in 2025. This replaces the previous threshold criteria for issuing alerts.

• Colour-coded weather alerts(Environment and Climate Change Canada, 2025)Canadians will be getting used to a new color-coded system of yellow, orange, and red weather alerts. This is the Environment and Climate Change Canada explainer page on how to interpret this new system. This webpage explains the colour coded approach to weather alerts, adopted in November 2025. Each warning, advisory, and watch weather alert has an associated colour when it is issued, and the colour goes from yellow, to orange, to red as the potential risk increases.

Health and safety precautions for extreme cold

• Extreme cold (Government of Canada, 2025)
  This webpage provides tips on what to do to prepare before extreme cold, how to respond during extreme cold, and signs of illness to watch for after extreme cold.

• Working in extreme cold (Government of Alberta, 2025)
  This infographicdepicts occupational safety considerations of working outdoors in extreme cold temperatures including prevention measures, how to recognize signs of cold exposure, and precautions employers and employees can take to reduce adverse health effects.

• Cold environments(Canadian Center for Occupational Health and Safety, 2025)
  This webpage outlines the health concerns and exposure limits for working outside in cold weather and provides guidance on minimizing cold injury through proper equipment design, safe work practices and appropriate clothing. 

• Warming centre guidance (Massachusetts Department of Public Health, Bureau of Climate and Environmental Health, 2024)
  This guidance document provides advice and best practice recommendations for US municipalities on setting up a warming centre, which could be adapted to Canadian settings.

• Safety guidelines: During and after a winter storm (US CDC, 2024)
  This webpage provides information on avoiding indoor hazards during an extreme cold event such as carbon monoxide poisoning, smoke inhalation, and fires, and advice on staying safe outside

• Supporting people who use substances during extreme cold events (Ontario Harm Reduction Distribution Program 2024)
  This guidance document explains the risks of extreme cold weather for people who use substances, signs and symptoms of cold-related illness, approaches to messaging, and how harm reduction programs can support service users during extreme cold weather.

• Public health recommendations to reduce the impacts of exposure to winter weather on people experiencing homelessness in British Columbia(BCCDC, 2023)
  This guidance document provides information on populations at risk of cold-related injuries due to exposure to cold weather conditions, and advice on preparing, and enacting a winter weather response plan for people experiencing homelessness.

• Severe winter weather and storm preparedness guide(PreparedBC, 2023)
  This guidance document available in English, French, Simplified Chinese, Traditional Chinese, and Punjabi provides advice on planning and preparing for winter weather.

• Cold-related emergencies: staying warm and safe in Canadian winters(Canadian Red Cross, 2022)
  This webpage provides guidance on how to prevent cold-related health emergencies for yourself, and how to recognize and help others who may be suffering from frostbite or hypothermia.

• Cold weather health risks and COVID-19 actions to prevent harm(UK Health Security Agency, 2021)
  This slide deck outlines the health impacts of cold weather and sets out harms of cold weather exposure and COVID-19 infection and proposes several strategies that public and environmental health and housing professionals can implement to prevent cold-related harm.

Additional research and literature on health effects of cold weather exposure

• Health impacts of cold exposure among people experiencing homelessness: A narrative systematic review on risks and risk-reduction approaches (Akhanemhe et al. 2025)
  This systematic review is the first systematic review to assess the association between cold weather exposure and health outcomes in people experiencing homelessness, and the literature on interventions to reduce these risks.

• Frostbite and hypothermia among individuals experiencing homelessness in the south interior region of BC: a chart review of emergency department presentations (Perrich et al, 2025)
  This peer reviewed article conducted a chart review of emergency department (ED) presentations for cold weather-associated health outcomes in the IH region and confirmed that people experiencing homelessness are at high risk of frostbite/cold injury and hypothermia, especially in urban areas.

• Emergency preparedness and extreme weather experiences of Indigenous people, 2024 (Statistics Canada, 2025)
  These survey results provide information on the emergency preparedness and extreme weather experiences among Indigenous people in Canada aged 15 years and older, including the impact of winter storms.

• Evidence-informed recommendations for municipal supports of people experiencing homelessness during extreme weather events (Trudeau et al, 2025)
  This peer reviewed article presents results of a policy scan of 40 Canadian and international municipalities and a literature review of interventions to assist people experiencing homelessness during extreme heat, extreme cold, or wildfire smoke events.

• Trends in emergency department visits during cold weather seasons among patients experiencing homelessness in Ontario, Canada: a retrospective population-based cohort study (Richard et al, 2024)
  This peer-reviewed article from Ontario, Canada reports on an increase in ‘non-urgent’ emergency department attendances over time (2018-2023) among people experiencing homelessness, suggesting a growing tendency to use healthcare facilities as temporary shelter during cold weather spells.

• A WISH to be Housed: Exploring the Winter Interim Solution to Homelessness (WISH) Temporary Accommodation Model in London, Canada (Smith-Carrier et al, 2022)
  This peer-reviewed article of a qualitative study analysing the experiences and perspectives of users of a temporary housing program, the Winter Interim Solution to Homelessness (WISH) in London, Canada, which used a barrier-free, harm reduction model.

• Cold weather conditions and risk of hypothermia among people experiencing homelessness: implications for prevention strategies (Zhang et al., 2019)
  This peer-reviewed article examines the association between cold weather and hypothermia among the homeless in Toronto (2004-2015). Results indicate that most hypothermic events occurred at temperatures above the city’s extreme cold threshold, suggesting that cold weather responses should be active all winter, and not only during extreme cold events.

• Climate change and temperature extremes: a review of heat- and cold-related morbidity and mortality concerns of municipalities(Gronlund et al., 2018)
  This narrative literature review examines the social and environmental risk factors that heighten vulnerability to cold- and heat-related morbidity and mortality and proposes both short- and long-term interventions that can be implemented at the municipal-level to reduce these risks.
   
• Characterizing the effects of extreme cold using real-time syndromic surveillance, Ontario, Canada, 2010-2016(VanStone et al., 2017)
  This peer-reviewed article investigates three extreme cold alerting algorithms using real-time syndromic surveillance of acute care patients to determine which algorithm best characterizes different populations according to the threshold temperature for which health effects occur.

• Effects of home energy efficiency and heating interventions on cold-related health (Milner & Wilkinson, 2017)
  This review examines the extent to which energy-efficient homes and heating interventions reduce the physical and mental health risks associated with cold temperatures and implications for public health policy.