Extreme Weather and UV Protection Guide

This guideline provides definitions of, information about potential injuries that can occur from, and strategies for protection from:

  • Extreme Cold Weather
  • Extreme Hot Weather
  • Ultraviolet (UV) Rays  

Extreme hot or cold weather conditions, as well as the level of the sun’s UV rays, may have an impact on the health and well-being of children and adults in our schools and workplaces. Weather conditions can change throughout the day. When weather conditions are questionable, staff can consult Environment Canada for information, as well as The Weather Network for their local forecast, including the UV index.

While there is no Board-wide temperature or UV Index threshold for the automatic suspension of outdoor activity based on weather conditions, it is important to bring an inherent awareness about extreme weather and precautions that can be taken to keep everyone safe, healthy and well. During extreme weather conditions, principals are responsible for responding to the individual needs of their students and staff. This may take the form of indoor recess breaks or changes in schedules for sporting events or any other action the principal deems appropriate to respond to the conditions.  The strategies suggested in this guideline should be incorporated into a school/workplace action plan and communicated to all students and staff. 

Note: This guideline does not include operational matters or strategies to deal with emergency preparedness. Information concerning such matters may be found in the Board’s Emergency Preparedness Policy and Procedure 669.



1. Extreme Cold Weather

When the temperature and/or wind chill are minus 20 degrees Celsius or below.  Extreme cold weather may include, but is not limited to, blizzards, freezing rain, ice pellets, rain, hail, heavy snow/squalls/blowing snow, ice, thunderstorms, lightning and extreme winds/wind chill.

2. Extreme Hot Weather

When the humidex is over 35 degrees Celsius. Extreme hot weather may include, but is not limited to, fog, hail, heat and humidity, lightning, thunderstorms and wind.

3. Ultraviolet (UV) Rays

Most of the UV radiation that reaches the earth’s surface is made up of UVA and UVB rays. The amount of UV radiation one receives depends on the level of the sun’s rays and the amount of time spent in the sun. Although the body can easily detect sunlight and heat, it cannot detect the level of UV radiation. When the UV index is six (6) or higher, protection is needed.



Extreme Cold Weather

Cold temperatures and the presence of ice and snow make winter in Canada a naturally more hazardous season. When severe weather occurs, such as blizzards, freezing rain or extreme wind chill, conditions that are already challenging can become even more dangerous. As with all severe and hazardous weather, knowing what to expect and how to prepare staff and students is essential.

How much heat you lose depends not only on the cooling effects of the cold and the wind chill, but on other factors. Your body type helps to determine how quickly you lose heat; people with a tall, slim build become cold much faster than those who are shorter and heavier. Age and physical condition also play a part. Elderly people and children have less muscle mass and as a result, generate less body heat. Sunshine, even on a cold winter day, can also make a difference. Bright sunshine can make you feel as much as ten (10) degrees warmer. Over time, bodies can also adapt to the cold. People who live in a cold climate are often able to withstand cold better than those from warmer climates.

Outdoor temperatures and shelter conditions vary substantially from school to school. Winter temperatures in the minus teens and even minus twenties are not uncommon for many Ontario students to face as they travel to and from school. Health authorities, such as York Region Public Health Services, advise that risks arising from cold weather come from prolonged exposure of unprotected skin.



  • Refer to Environment Canada’s Information about Cold Weather or Environment Canada's Information about Wind Chill Index

  • Ensure that all staff, students and parents/guardians are made aware whenever the action plan is activated.

  • Students with health concerns, such as, but not limited to, heavy colds, coughs and flu, which are serious enough to prevent them from participating in physical education, recesses or other outdoor activities, should remain at home until the condition improves.

  • Students are to come to school ready for winter and prepared to be outdoors after lunch.

  • When temperatures and/or wind chill reach minus 20 degrees Celsius, consider an indoor routine for recess/events.

  • When temperatures and/or wind chill reach minus 18-19 degrees Celsius, consider a shortened outdoor routine for recess/events.

  • Children need to be dressed properly for our invigorating winter days. It is advisable for students to bring extra pants and socks. A change is often necessary due to the wet and cold weather of the winter months. To avoid adding to the clothing collection in the Lost and Found, parents/guardians should be advised to label all articles of clothing, including but not limited to, boots, hats, mitts/gloves, scarves, and snow pants.

  • Encourage physical activity, such as walking or playing, to increase metabolism – which generates more body heat.

  • Children should be monitored closely for signs of frostnip, frostbite or difficulty breathing.


Cold Injuries

Exposure to the cold can be hazardous or even life-threatening. The body's extremities, such as the ears, nose, fingers and toes, lose heat the fastest. Exposed skin may freeze, causing frostnip or frostbite. In extreme conditions or after prolonged exposure to the cold, the body core can also lose heat, resulting in hypothermia.



  • Being cold over a prolonged period of time can cause a drop in body temperature (below the normal 37 degrees Celsius).

  • Shivering, confusion and loss of muscular control, such as but not limited to difficulty walking, can occur.

  • May occur from immersion in cold water.

  • It can progress to a life-threatening condition where shivering stops or the person loses consciousness. Cardiac arrest may occur.

What to do:
  • Get medical attention immediately.

  • Lay the person down and avoid rough handling, particularly if the person is unconscious.

  • Get the person indoors.

  • Gently remove wet clothing.

  • Warm the person gradually and slowly, using available sources of heat.



  • A mild form of frostbite, where only the skin freezes.

  • Skin appears yellowish or white, but feels soft to the touch.

  • Painful tingling or burning sensation.

What to do:
  • Do not rub or massage the area.

  • Warm the area gradually using body heat (a warm hand) or warm water. Avoid direct heat which can burn the skin.

  • Once the affected area is warm, do not re-expose it to the cold.



  • A more severe condition, where both the skin and the underlying tissue (fat, muscle, bone) are frozen.

  • Skin appears white and waxy and is hard to the touch.

  • No sensation or numbness to the area.

What to do:
  • Get medical help.

  • Frostbite can be serious, and can result in amputation.

  • Do not rub or massage the area.

  • Do not warm the area until you can ensure it will stay warm.

  • Warm the area gradually; use body heat, or warm water (40°C to 42°C). Avoid direct heat which can burn the skin.

Extreme Hot Weather

Warm weather brings with it enjoyable activities, but hot weather can also cause stress to our bodies. The Ministry of Labour has developed guidelines to deal with heat stress; however, there is no upper limit for temperature in the workplace. The guidelines are intended for use in workplaces where the main contributor to high heat is within the process of the work or where the work is physically demanding. Heat related stress can also be brought on by higher ambient temperatures and humidity levels.

Most people feel comfortable when the temperature ranges from 18 to 22 degrees Celsius and when relative humidity is about 45 per cent. When ambient temperatures climb over 35 degrees Celsius and high humidity combines to make it feel higher, the body’s ability to cool itself becomes increasingly difficult. Unlike process heat which allows one to become acclimatized, the short duration of hot days does not usually allow this to occur. Some individuals are more susceptible to heat related illness such as children less than 15 years old, seniors 65 years and older, playing sports or engaging in prolonged physical exertion, wearing excessive/heavy clothing and people on certain medications (especially those used to control epilepsy or psychotic disorders). It is very important that each school has an action plan to address student and staff needs during periods of extreme hot weather.

Precautions can be taken on very hot days to protect both students and staff from heat related illnesses. Heat stress is affected by four (4) environmental factors; air temperature, humidity, air movement and radiant heat. Individual factors such as age, existing medical and physical conditions also play a part in how an individual copes during times of extremely hot weather.

Hot weather plans should be activated when the following weather/environmental triggers occur:

  • the humidex reaches or exceeds 35 degrees Celsius;

  • the combination of a smog alert and higher temperatures;

  • during heat waves; or

  • three or more days of temperatures 32 degree Celsius or higher;



  • Refer to Environment Canada’s Information on Humidity and Humidex and their strategies for summer comfort. 

  • Ensure that all staff, students and parents/guardians are made aware whenever the hot action plan is activated.

  • If possible. reschedule outdoor/indoor physical activities to cooler times of the day or on another day when the humidex is under 35 degrees Celsius.

  • Encourage students and staff to make use of shady areas in the school yard such as under trees, beside the building and under umbrellas.

  • Keep blinds/curtains closed in classrooms directly exposed to sunlight and turn off any unnecessary lights.

  • For hot, humid weather relief in classrooms or portables, Board-approved fans may be used to provide air movement in the room. Some classes may have to be relocated to cooler areas such as gymnasiums or libraries to provide relief.

  • Educate students and parents about the need to wear loose, light clothing that covers their arms and legs, which will help to reduce body heat through moisture evaporation.

  • Encourage the drinking of water for rehydration after excessive fluid loss during physical activities or on hot, humid days. Avoid using carbonated drinks with caffeine which promote excessive fluid loss. Drink water before exercise and every 15-20 minutes during exercise. Drink water regularly throughout the day to maintain hydration.


Heat Related Illnesses

The majority of heat related illnesses such as fainting, heat cramps, and heat exhaustion are considered minor. Although not life threatening like heat stroke, they are important to recognize and prevent. Physical activity can be a contributor to heat related illnesses; however it is usually the result of physical activity combined with excessive heat retention and dehydration that causes health issues.

The following are some of the signs, symptoms, causes and first-aid treatments for heat related illnesses:


Heat Related Fainting

  • Signs and symptoms are dizziness, fatigue, irritability, lack of concentration and loss of the ability to make rational decisions.

  • Caused by the body’s attempt to increase blood flow at skin surfaces in order to reduce body temperatures; resulting in lower blood flow to the brain.

  • First-Aid may include moving to a cooler area, loosening clothes and drinking cool water.


Heat Related Cramps

  • Signs and symptoms are painful arm, leg or stomach muscle spasms, thirst, heavy sweating; may occur after prolonged physical exertion.

  • Caused by loss of water and body salts.

  • First-Aidmay include drinking water, loosening clothing, resting in a cool location and lightly stretching the affected muscles. Avoid drinking anything with caffeine, such as most cola drinks, tea or coffee


Heat Exhaustion

  • Signs and symptoms include those of early heat related fainting plus loss of coordination, collapse, heavy sweating, cool, moist, (clammy), pale skin, dry mouth with excessive thirst, fast pulse, and low to normal temperature.

  • Causesare reduced blood circulation and flow to the brain and dehydration.

  • First-Aidmay include slowly giving the person cool water to drink (a half glass of water every 15 minutes is best), have them lie down in a cool area, loosen or remove clothing or hat, splash cool water on body and massage arms and legs. If the person does not show improvement in 10 to 15 minutes, call for emergency medical assistance.


Heat Stroke (Call 911 immediately)

This is the most severe form of heat related illness and is life threatening. Core body temperature may reach and exceed 40 degrees Celsius. It can even occur in people who are not involved in physical activities or exercise during hot, humid weather.

  • Signs and symptoms are dizziness, confusion, headaches, irrational behaviour, loss of consciousness, reduced or no sweating, fast pulse rate, rapid breathing, convulsions, nausea and vomiting.

  • Causesare dehydration, sustained physical exertion, reduced blood flow to critical parts of the body such as, but not limited to the brain and heart; body has lost ability to cool itself, and overexposure to high temperatures even without exertion.

  • First-Aidmay include moving to a cool or shaded area, removing shoes and outer clothing, wrapping in wet cloths, splashing or spraying water onto the skin, fanning rapidly, elevating the legs and clearing vomit to prevent choking. Give water to drink if the person is conscious. If the person is not conscious or refuses water, do not force them to drink. Wait for emergency medical help to arrive.

It is important to remember that hyperthermia occurs along a continuum starting with heat stress and progressing to heat exhaustion and stroke. If the first signs of heat stress are not dealt with, it can lead to further deterioration and ultimately heat stroke. Heat stroke is a medical emergency with a need to call 911. If there is a person available with first aid training they may respond to the more minor illness; however, anyone can follow the above steps and successfully assist a person suffering from heat related illness.

Ultraviolet Rays

Ultraviolet (UV) rays are the sun’s rays that can cause sunburn. Long-term exposure to UV rays is associated with skin aging, eye cataracts, weakening of the immune system, and skin cancer.

The amount of UV that you receive depends on both the strength of the sun's rays (measured by the UV index) and the amount of time you spend in the sun. The higher the UV Index number, the stronger the sun's rays, and the greater the need to take sun safety precautions. The UV Index is a 0 - 11+ scale  .Note: UV protection may be needed in cold weather as well as in hot weather.



  • Refer to Environment Canada’s UV Index and Sun Safety and How to Use the UV Index

  • Communicate with students, staff and parents/guardians the need to take precautionary measures to avoid the sun’s rays when the UV Index is high.

  • When the UV Index is six or over, continue with a regular outdoor routine for recess/events with precautionary measures.

  • Raise awareness about wearing protective clothing (with UV protection if the index is at 6 or higher), hats (wide brimmed), sunglasses and broad spectrum sunscreen with a sun protection factor (SPF) of 30 or higher.


UV Related Injuries

Sunburns result from too much sun or sun-equivalent exposure. Sunburn is a form of radiation burn that affects living tissue that results from an overexposure to ultraviolet radiation from the sun.



  • Signs and symptomsinclude, but are not limited to, skin redness and pain, blistering, dehydration, chills, fever, nausea, vomiting and peeling of the skin.

  • Causesinclude, but are not limited to, unprotected exposure to ultraviolet radiation.

  • First-Aidmay include covering the exposed skin, applying sunscreen and staying hydrated. For mild sunburn, applying a cool compress and lotion to the affected skin can reduce the pain associated with sunburn


Additional Information: