Heat Warning Issued: Dangerous Heat and Humidity Beginning Sunday Across Ontario
- Small Town Productions
- Jun 21
- 3 min read
Updated: 7 days ago
June 21, 2025
UPDATE: HEAT WARNING EXTENDED UNTIL JUNE 25TH AT 2:22AM
Disclaimer: We do not create the weather warnings/alerts, we just choose to report them when they are announced from Environment Canada for the vulnerable populations (seniors, children, animals/pets, etc.).
Environment Canada has issued a heat warning for much of Ontario as the region braces for its first significant heat event of the season. Beginning Sunday afternoon, dangerously high temperatures and humidity levels are expected to persist through at least Tuesday night, with a possibility of extending into Wednesday in parts of southwestern Ontario and the GTA.
🔥 What to Expect:
Daytime highs: 31°C to 36°C
Humidex values: 40 to 45 — meaning it will feel more like 40°C to 45°C with the humidity
Overnight lows: 21°C to 25°C — offering little nighttime relief
These humidex values reflect the perceived temperature when humidity is factored in, significantly increasing the risk of heat-related illness.
This type of extreme heat can pose serious health risks, especially to vulnerable individuals such as older adults, young children, those with pre-existing health conditions, and people without access to air conditioning.
🕑 Duration:
Start: Sunday afternoon, June 22
End: Tuesday night, June 24
May extend into Wednesday, depending on the movement of a cold front approaching mid-week.
⚠️ Take Action to Stay Safe:
Check on others, especially seniors, those living alone, or anyone who may be vulnerable.
Watch for early signs of heat exhaustion, such as:
Headache, nausea, dizziness
Fatigue, thirst, or dark urine
If you experience these symptoms, stop all activity and drink water.
🚨 Heat Stroke is a Medical Emergency:
Call 9-1-1 immediately if someone is experiencing:
Confusion, loss of consciousness
Red, hot skin or profuse sweating
Rapid breathing or nauseaWhile waiting for help: Move the person to a cool area, remove excess clothing, and apply cold water or ice packs.
💧 How to Stay Cool:
Drink water frequently, even before you feel thirsty.
Avoid outdoor activities during peak heat—plan for mornings or evenings instead.
Wear lightweight, loose-fitting clothing and a wide-brimmed hat.
Keep blinds closed and windows open if the outdoor air is cooler.
Use fans or air conditioning where available.
Visit cooling centres, libraries, or community centres if your home is too hot.
Never leave people or pets in parked vehicles. Double-check the back seat before locking your car.
📡 Stay Informed:
Continue monitoring Environment Canada alerts.
Report severe weather via email to ONstorm@ec.gc.ca or on X (formerly Twitter) using #ONStorm.
📢 Share to Keep Others Safe
Extreme heat can catch people off guard. Please share this heat warning with your family, friends, and neighbours—especially those who may not be online. A quick message, a knock on a door, or a phone call can make a huge difference in helping someone stay safe.
Use social media, community groups, or even a simple text to spread the word and remind others to check on loved ones and take steps to stay cool.
Together, we can help prevent heat-related illnesses and protect our most vulnerable during this extreme weather event.
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