» Health Information » Emergency Preparedness » Severe Weather » Tornadoes

Tornadoes

This page was reviewed or revised on Thursday, July 2, 2015 9:21 AM

A tornado is a column of rotating wind, travelling across the land at up to 100 km/h. Wind speeds within a tornado can range from 64 km/h to over 500 km/h.

Most tornadoes in Ontario occur from May to September in late afternoon and are most frequent during moderate summer temperatures, accompanied by high humidity.

Warning signs that may precede a tornado:

• Thunderstorms that grow in intensity, with heavy rain and severe thunder and lightning;
• Large hail (hail larger than a nickel is evidence of a very strong storm);
• An extremely dark sky, sometimes highlighted by rotating green or yellow clouds;
• Unusual darkness and an eerie calm at the end of a severe storm;
• A rumbling sound like a freight train, or a whistling sound like a jet.

If you observe any of the above warning signs, take cover immediately!

Be Prepared: Be Aware of Watches and Warnings

Environment Canada will issue tornado Watches or 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 tornado WATCH is issued if conditions are favourable for tornadoes to develop later in the day. A tornado has not been sighted when a watch is issued. A watch is usually issued early in the day, so monitor weather conditions and listen for updated weather reports.
• A tornado WARNING is issued if one has been sighted, or if radar detects a tornado-like disturbance. Residents in the area covered by a warning will usually be advised to take shelter immediately!

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

What to do when a tornado threatens

Take shelter immediately, preferably in the lowest level of a sturdy building.
Stay away from windows, outer doors and exterior walls. Flying glass and debris blown into a building are extremely dangerous.

Do not spend valuable time opening windows to prevent a building from "exploding." Such action is unlikely to help because buildings are damaged by wind and by debris blown by the wind - not by a sudden drop in air pressure.

Take cover immediately when advised or when conditions dictate.

Finding shelter

In a house, go to the basement and take shelter under a stairway or a sturdy work table.

In a house with no basement, go to a hallway, a closet or a bathroom near the centre of the house. Lying in a bathtub with a mattress on top may provide additional protection.

In a large building such as a grocery store or shopping mall, go to an interior hallway or a washroom on the lowest level or get under a sturdy piece of furniture. Avoid large rooms and stay away from windows.

In high-rise buildings, go to the lowest level, a small interior room or a stairwell. Stay out of elevators and away from windows.

In a vehicle or mobile home, find other shelter immediately. If better shelter is not available, lie in a ditch or culvert, but be aware of flash flooding. Protect your head and watch out for flying debris.

If you are driving and see a tornado in the distance, try to find shelter. If the tornado is close, get out of your vehicle and take cover in a low-lying area. If a tornado seems to be standing still, it is either travelling away from you, or heading right toward you!