Extreme Weather – Heat
A Harmonized Warning and Information System
Environment and Climate Change Canada, working together with Health Canada, the Ontario Ministry of Health and Long-term Care and Ontario’s Public Health Units, developed a harmonized heat warning information system starting in 2016.
This extreme heat warning system is based on a combination of the latest in health science, Ontario-specific health evidence, and a detailed analysis of weather patterns in Ontario. The province has been divided into three regions: northern, southern, and extreme south-west (Windsor) area, each with its own updated, region-specific temperature and humidex criteria.
Environment and Climate Change Canada issues Heat Warnings 18 to 24 hours in advance of the heat event. Forecasters will assess if two or more consecutive days of weather that meet either the humidex or temperature criteria (daytime highs or nighttime lows) are expected in the region. If so, a Heat Warning will be issued.
The Ontario Heat Warning Protocol incudes two warning levels:
Level 1: Heat Warning
A Heat Warning is issued when two consecutive days are forecasted to have a daytime high temperature greater than or equal to 31C AND a nighttime temperature greater than or equal to 20C or a humidex greater than 40. This level of reminds residents of the following core messages: to keep their home cool, stay out of the heat, keep the body cool and hydrated, assist others, and recognize the symptoms of heat exhaustion.
Level 2: Extended Heat Warning
An Extended Heat Warning will be issued for a heat event lasting three or more days. This level of warning reminds residents of the core messages above, in addition to providing details on how and where to stay cool, advising suspension of strenuous outdoor activities, reminders to assist vulnerable groups, and to watch for further information through the media and the Public Health website.
Extreme heat events are a potentially significant health risk and can have a severe impact on the health of vulnerable populations including infants, the elderly, shut-ins, persons with chronic diseases, the morbidly obese and the marginally housed. Heat related illnesses such as dehydration, heat cramps, heat exhaustion, and heat stroke are preventable. Most healthy people can tolerate a short period of hot and humid weather as long as they stay cool and drink plenty of fluids. It is important to be aware that some medications may increase the health risks from extreme heat events.
Peterborough Public Health encourages all stakeholders to advise vulnerable clients of the heat advisory system and precautions they can take to prevent and manage heat related illness.
How to Protect Yourself During Hot Weather:
- Drink lots of water and natural fruit juices even if you don’t feel very thirsty. Avoid alcoholic beverages, coffee and cola.
- Avoid going out in the direct sun or heat when possible. If you must go outside, stay in the shade as much as possible and plan to go out early in the morning or evening when it is cooler.
- Go to air conditioned or cool places such as shopping malls, libraries, community centres or a friend’s place.
- If you don’t have air conditioning, keep shades or drapes drawn and blinds closed on the sunny side of your home, but keep windows slightly open.
- Wear loose fitting, light clothing and a wide brimmed hat.
- Keep lights off or turned down low.
- Take a cool bath or shower periodically or cool down with cool, wet towels.
- Avoid heavy meals and using your oven.
- Avoid intense or moderately intense physical activity.
- If you are taking medication or have a health condition, ask your doctor or pharmacist if it increases your health risk in the heat and follow their recommendations.
Symptoms of heat exhaustion include:
- heavy sweating
- muscle cramps
- paleness, tiredness
- dizziness, nausea
Air conditioned public facilities are available to city and county residents seeking a place to cool off, such as shopping malls, community centres, arenas and libraries. Residents are advised to phone the cooling centres in advance to determine hours of operation.