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Durham Region: Heat Warning and Information System (HWIS)

To help Durham Region residents take protective action during extreme heat events, Durham Region Health Department has implemented the Durham Region Heat Warning and Information System (HWIS).

The Durham Region HWIS can reduce heat-related illnesses during extreme heat events by alerting the public about extreme heat events, directing community response and outreach to vulnerable and priority populations, and providing individuals with information on how to prevent heat-related illnesses.

Heat and health

Extreme heat and humidity puts everyone at risk of heat-related illnesses. It is important to protect yourself and your family during extreme heat events. Your age and health may make you more susceptible to heat related illness.

•You can become ill while being active during extreme heat. Try to reschedule or plan outdoor activities during cooler parts of the day.

•Remember to frequently call, text or video call and check in with neighbours, friends and older family members, especially those who are chronically ill, to ensure that they are cool and hydrated. If that is not possible, be sure to practise physical distancing.

Never leave infants and young children inside a parked vehicle. This is especially important as when the outside air temperature is 23ºC/73ºF, the temperature inside a vehicle can be extremely dangerous and reach more than 50ºC/122ºF. Anyone seeing a child left unattended in a hot vehicle at anytime should call 911 immediately.

Symptoms of heat illness:

•Heat edema (swelling of hands, feet, and ankles).

•Dizziness or fainting.

•Nausea or vomiting.


•Fast breathing and heartbeat.

•Extreme thirst.

•Less urination and very dark yellow urine.

•Changes in behaviour (sleepiness or temper tantrums in children)

Common heat illnesses:

•Heat edema (swelling of hands, feet, and ankles).

•Heat rash.

•Heat cramps.

•Heat fainting.

•Heat exhaustion.

•Heat stroke.

Heat stroke symptoms:

•High body temperature.



•Not sweating.

•Signs of heat illness.

While waiting for medical help, you should:

•Move yourself or the person to a cool place, if possible.

•Place cold water on skin or clothing.

•Fan yourself or the person.

How to cool down and when to seek emergency help

Your body cools down by sweating. Your sweat cools your body as it evaporates. The weather affects how you stay cool. If it’s windy, sweat evaporates faster, which helps to cool you faster. High humidity slows your body’s ability to cool down.

If you are feeling any of these symptoms in hot weather, you should:

•Move to a cool place such as an air-conditioned room or under some shade.

•Drink sips of water or other liquids.

•Cool off by taking a cold shower or using a fan.

You are at greater risk if you:

•Are a senior.

•Are an infant or child.

•Have an existing illness (difficulty breathing, diabetes, heart condition, mental illness).

•Work outside.

•Exercise outside.

•Are homeless.

•Live by yourself and have problems with movement.

•Are on medication that affects how you deal with heat.

You can protect yourself and try to prevent heat and humidity related illnesses by:

•Checking weather forecasts for hot weather and Environment Canada for heat warnings (

•Checking if your air conditioner works before hot weather starts.

•Making your home cooler by planting trees for more shade.

•If you have no air conditioner, find a place to cool off during hot weather.

•If you take medication, check with your doctor to find out how extreme heat may affect you.

•If you have no air conditioning or have a medical condition, then have family, friends, and neighbours call and check in on hot days to make sure you are okay.

•Staying hydrated by drinking lots of fluids, especially water.

•Wearing loose fitting clothing while outside.

•Covering exposed skin when out in the sun.

•Wearing a wide-brimmed hat when in the sun.

•Wear sunglasses with UVA and UVB protection for your eyes.

•Using an umbrella for shade.

•Using a sunscreen with SPF30 or higher.

•As a last resort, seek shade as it can reduce the temperature outside by 5°C.

•Schedule your outdoor time during cooler times of day (morning and night).

•Check the Air Quality Health Index as air pollution can be higher during very hot days.

•Reschedule your plans for a cooler day or choose a location with shade or air conditioning near you.

If you must work outside or do physical activity in extreme heat, take extra precautions:

•Take extra breaks.

•Drink lots of water.

•Wear less gear, if possible.

•Ensure to maintain physical distancing and stay 2 metres (6 feet) apart from co-workers and others.

There are ways to keep your home cool even without an air conditioner:

•Try cooking outside instead of using the stove or oven.

•Close curtains or blinds during the day.

•If the night is cooler, open windows to cool home.

Use your air conditioner. If you are using a window air conditioner, cool the one room you will use for a heat break.

If your home is extremely hot:

•Take cool showers.

•Use a fan.

•Visit a place with shade, a pool, or an air conditioned space while ensuring to maintain physical distancing (2 metres or 6 feet apart) from others at all times.

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