What constitutes cold stress and its effects can vary across different areas of the world. In regions relatively unaccustomed to winter weather, near freezing temperatures are considered factors for cold stress. Whenever temperatures drop decidedly below normal and as wind speed increases, heat can more rapidly leave your body. These weather-related conditions may lead to serious health problems.^{3 3}Cold Stress | NIOSHX

Extreme cold can result in various serious health impacts, including:

Hypothermia: When exposed to cold temperatures, your body begins to lose heat faster than it can be produced. Prolonged exposure to cold will eventually use up your body’s stored energy. The result is hypothermia, or abnormally low body temperature. A body temperature that is too low affects the brain, making the victim unable to think clearly or move well. This makes hypothermia particularly dangerous because a person may not know it is happening and will not be able to do anything about it.^{4 4}Cold Related Illnesses | NIOSHX

Frostbite: Frostbite is an injury to the body that is caused by freezing. Frostbite causes a loss of feeling and colour in the affected areas. It most often affects the nose, ears, cheeks, chin, fingers, or toes. Frostbite can permanently damage body tissues, and severe cases can lead to amputation. In extremely cold temperatures, the risk of frostbite is increased in those with reduced blood circulation and among those who are not dressed properly.^{5 5}Cold Related Illnesses | NIOSHX

Trench Foot: Trench foot, also known as immersion foot, is an injury of the feet resulting from prolonged exposure to wet and cold conditions. Trench foot can occur at temperatures as high as 15 degrees Celsius if the feet are constantly wet. Injury occurs because wet feet lose heat 25-times faster than dry feet. Therefore, to prevent heat loss, the body constricts blood vessels to shut down circulation in the feet. Skin tissue begins to die because of lack of oxygen and nutrients and due to the buildup of toxic products.^{6 6}Cold Related Illnesses | NIOSHX

Other related direct and indirect risks include:

• Falls and injuries
• Respiratory infections and influenza
• Chilblains
• Heart problems, including heart attacks and strokes
• Raynaud’s phenomenon
• Cold-induced urticaria
• Mental health problems such as depression
• Carbon monoxide poisoning
• Joint pain

During cold weather, the body’s heart rate is increased and blood is pumped faster around the body to maintain warmth. This high heart rate and blood pressure is unsustainable and can increase the risk of heart attacks. A drop in body temperature as little as 2°C can prevent vital organs from functioning correctly, leading to organ failure. Cold temperatures can worsen conditions including heart disease and respiratory illness.

Cold weather can also result in reduced blood supply to the extremities, and the reduction in blood flow means the immune system is compromised and there may be an increased susceptibility to infections, such as rhinovirus and influenza.

Air-borne diseases such as influenza and norovirus are more common in colder conditions as a result of heating and poor ventilation that provide optimal conditions for viral spread, combined with close contact between people.

Hazardous icy conditions caused by extreme cold are a direct health hazard and can cause falls and injuries that result in an increased number of sprains and broken bones.

Carbon monoxide poisoning can result from poorly maintained boilers, cooking and heating appliances.

• Advanced age, illnesses and medications may make the elderly more susceptible to hypothermia
• Young children lose heat more quickly than adults.
• Those with pre-existing medical conditions, such as asthma and cardiovascular disease.
• Outdoor workers.
• People experiencing homelessness, living in homes with inadequate heating or who are socially isolated.
• The mentally impaired, including those with dementia, may not fully realize the danger of going outside in cold weather not properly dressed.
• Those under the influence of alcohol or drugs, which lower the body’s ability to retain heat and impairs judgment.

Climate change is projected to decrease cold-related mortality due to fewer cold extremes.^{7 7}Gasparrini et al., 2017X On the other hand, several studies ^{8 8}Ebi and Mills, 2013, Kinney et al. 2015, Staddon et al. 2014X have questioned the assumption that the seasonal variation in mortality would be attributable to temperature only. Higher winter mortality may also be related to other factors that vary seasonally such as influenza epidemics and solar radiation. Some studies have shown a decrease in population susceptibility to heat over time, but a similar decrease in susceptibility to cold is not found.^{9 9}Arbuthnott et al., 2016X The long-term adaptation of population to gradually warming climate, and changes in sensitivity of people to extreme temperatures cause substantial uncertainty in projected changes in cold-related health impacts.

National Meteorological Services should issue cold weather and wind chill warnings to enable communities, workplaces and individuals to manage risk.

Governments should ensure power is not cut off during cold weather, and incentivize energy efficiency in homes and buildings.

Employers should implement a cold-related illness and injury prevention program that includes preventive measures such as using engineering controls, establishing work / rest schedules, training workers about the hazards of working in cold environments, and providing appropriate cold-weather gear.^{10 10}Preventing cold-related illness, injury, and death among workers. Jacklitsch B, Ceballos D. NIOSH. 2019X

Individuals should prepare for and dress for the cold. Emergency kits including supplies for cold weather can be kept on hand and in vehicles. Those living climates prone to cold weather should ensure their homes are well insulated with weather-tight windows and doors, and that their heating and plumbing systems are in working order.

Emergencies: If a person is experiencing signs of hypothermia and medical care is not available, warm them slowly, starting with the body core. Warming the arms and legs first drives cold blood toward the heart and can lead to heart failure. If necessary, use body heat to help. Get the person into dry clothing and wrap in a warm blanket covering the head and neck. Do not give the person alcohol, drugs, coffee or any hot beverage or food. Warm broth is the first food to offer.^{11 11}NWS: Stay Safe in the Extreme ColdX