Severe Weather

Severe Thunderstorms

Thunderstorms develop in a warm, humid, unstable air, most often between May and September. Storms usually only last an hour, but a line of thunderstorms can last for several hours.

Severe thunderstorms are often accompanied by hail, lightning, high winds, heavy rain, and potentially, tornadoes. That's why it is recommended people take the same precautions during a severe thunderstorm as they should during a Tornado Warning.

Be Prepared:  Be Aware of WATCHES and WARNINGS

Environment Canada will issue severe thunderstorm Watches and Warnings when appropriate and local radio stations will usually broadcast such advisories as soon as possible.

There are significant differences between Watches and Warnings:

A severe thunderstorm WATCH is issued if conditions exist for thunderstorms to develop. A Watch is usually issued early in the day, so monitor weather conditions and listen for weather reports.

A severe thunderstorm WARNING is issued for areas in the path of a storm that has intensified to the severe stage. Severe thunderstorm Warnings imply the risk of tornadoes, so residents should be prepared to take shelter if threatening conditions are present.

When weather conditions look threatening, turn on your radio and listen for weather reports.  If residents in your area are advised to take cover, do so immediately!

Lightning

The air is charged with electricity during a thunderstorm and this is seen as lightning. Bolts of lightning hit the ground at about 40,000 kilometres per second - so fast that the lightning appears to be a single main bolt with a few forks.  The main bolt is actually a series of lightning strikes, all taking the same path, but so fast and bright that the eye cannot distinguish between them.

To estimate how far away the lightning is, count the seconds between the flash of lightning and the thunderclap.  Each second is about 300 metres. If you count fewer than 30 seconds, look around for shelter; if you count fewer than five  seconds, take shelter immediately - lightning is near and you do not want to be the tallest object in the area. It is recommended that you wait 30 minutes after the last lightning strike before venturing outside again.

Lightning Safety

• If indoors, stay there, but away from windows, doors, fireplaces, radiators, stoves, sinks, bathtubs, appliances, metal pipes, telephones and other materials which conduct electricity.
• Unplug radios and televisions (use your battery-powered radio to listen to weather reports).
• If outdoors, take shelter in a building or a vehicle.  If this is not possible, get into a depressed area such as a ditch or a valley, but never under a tree.
• If swimming or out in a boat, get back to shore immediately.
• If caught in the open, do not lie flat - crouch down, lower your head and cover your ears with your hands.
• If you are in a vehicle, pull away from trees and hydro poles which might fall on you.  Do not touch anything metal inside the vehicle (it's the metal body surrounding you that protects you from lightning, not the rubber tires).

"When the sky roars, get indoors!"

Environment Canada recommends, "If you can hear thunder, seek your best shelter immediately and remain in that shelter for a full 30 minutes after the last thunder to ensure the storm has moved off.  Or more simply put, "When the sky roars, get indoors" - and remain there for a full 30 minutes after the last rumble of thunder."

Environment Canada - Weather Office

Local Weather Conditions Phone: 519 464-5121

Weather Warning Information

Severe Weather Watcher Handbook

Click on the PDF file below to learn more about what actions you should take during severe weather.

For current weather forecasts visit The Weather Network or Environment Canada.

Severe_Storms.pdf