Extreme Heat

Extreme heat events can put the public at risk of heat-related illnesses.

Heat Alerts

The Grand Erie Health Unit’s Medical Officer of Health will issue a Heat Alert or an Extended Heat Alert when extreme heat thresholds have been met. Subscribe to receive Weather Alerts by email.

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Extreme heat effects

Knowing the risks and how to protect yourself and your family will keep you safe over the summer. When out in the heat, watch for symptoms of heat illness, which include:

dizziness or fainting
nausea or vomiting
headache
rapid breathing and heartbeat
extreme thirst
decreased urination with unusually dark yellow urine

If you experience any of these symptoms during extreme heat, immediately move to a cool place and drink liquids. Water is best.

Heat stroke is considered the most serious heat-related illness and can result in death if not addressed quickly. Symptoms of heat stroke include a high body temperature, confusion, and fatigue. If you suspect you or someone else is experiencing heat stroke, call 911 immediately.

Who is most at risk?

Infants and young children
Pregnant women
Older adults
People with certain chronic illnesses, such as breathing difficulties, heart conditions, or psychiatric illnesses
People under the influence of drugs or alcohol
People who have mobility constraints
People who work or exercise outside
Socially disadvantaged individuals such as those who are isolated, have low income or are homeless
Newcomers to Canada (e.g. tourists, immigrants) that may not be acclimatized

Heat-related illnesses

Review heat-related illnesses and their symptoms.

Heat Stroke

Most serious type of heat illness as a result of body heat overload. Signs of heat stroke include a core body temperature of more than 40C/104F, complete or partial loss of consciousness and/or reduced mental ability. Sweating is not a good indicator as there are two types of heat stroke:

Classic- accompanied by little or no sweating, usually occurring in children, those who are chronically ill and older adults.
Exertional- accompanied by an increase in core body temperature because of strenuous exercise or occupational exposure in combination with environmental heat and where sweating is usually present.

Heat Exhaustion

Caused by excessive loss of water and salt. Symptoms include heavy sweating, weakness, dizziness, nausea, headache, diarrhea and muscle cramps.

Heat Fainting

Caused by the loss of body fluids from sweating and from lowered blood pressure due to pooling of blood in the legs. Symptoms include temporary dizziness and fainting resulting from an insufficient flow of blood to the brain while the person is standing.

Heat Cramps

Caused by a salt imbalance resulting from a failure to replace salt lost through excessive sweating. Symptoms are sharp muscle pains.

Heat Rash

A result of inflammation of clogged sweat glands and accompanied by tiny red spots on the skin which may give a prickling sensation.

Heat Edema

Heat induced swelling frequently noticeable in the ankles, feet and hands and most often seen in people who are not regularly exposed to heat.

How to stay safe

Stay hydrated

Drink plenty of cool liquids, especially water, before you feel thirsty

Dress for the heat

Wear loose-fitting, light-coloured clothing made of breathable fabric
If you need to be outdoors, wear a wide-brimmed, breathable hat or use an umbrella

Plan your day

Schedule outdoor activities during the cooler parts of the day, such as early morning or evening
Stay in the shade as much as possible when outside

Know your health risks

If you take medication or have a health condition, ask your doctor or pharmacist if heat increases your risk and follow their advice

Keep others safe

Never leave people or pets in a parked vehicle or in direct sunlight
Check on neighbours, friends and family members—especially older adults, those who live alone, or people with chronic illnesses—to make sure they are staying cool and hydrated

Keep cool indoors

Take cool showers or baths until you feel refreshed
Block the sun by closing awnings, curtains or blinds during the day
Take a break from the heat by spending time in a cool indoor space

The following locations can help you stay cool.

Air condition

Norfolk County Public Libraries - Check olc.ncpl.on.ca for locations and hours of operation.
Waterford Tricenturena Arena - 32 E Church Street, Waterford. Check norfolkcounty.ca/skating for hours of operation.

Pools

Annaleise Carr Aquatic Centre – 182 South Drive, Simcoe (closure in place for 2026)
Delhi Kinsmen Pool – 336 Talbot Road, Delhi

Swim programs and schedules vary. Admission rates apply. Visit norfolkcounty.ca/swimming for details.

Splash pads

Simcoe Kinsmen Splash Pad – 281 Head Street North, Simcoe
Delhi Splash Pad – 336 Talbot Road, Delhi

Visit norfolkcounty.ca/swimming for hours of operation.

Causes of extreme heat

Four environmental factors work together to make it hot enough to endanger health:

High temperature, high relative humidity (moisture in the air)
Radiant heat (from the sun)
Low wind speed (lack of air movement)

Additionally, an individual’s health can depend on their sensitivity, acclimatization, and their own, as well as their community’s, adaptability to extreme heat.

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