Thunderstorms

Summer thunderstorms are a fairly common occurrence in most areas of Canada, providing much-needed precipitation for gardens, crops, and other purposes. Unfortunately, a small percentage of summer thunderstorms intensify to the extent that they become "severe", causing damage to property and threatening lives.

Environment Canada will issue a severe thunderstorm or tornado warning if heavy rain, high winds, tornadoes, hail or intense lightning are present or expected. The storm's expected motion and developments are also provided in the weather warning. If you hear a weather warning and are in the area specified, take appropriate precautions.

General Precautions

The following general precautions offer advice on how you can plan in advance to cope more safely with a severe thunderstorm.

• Choose a shelter in advance. Good places to be during severe storms are basements, storm cellars, and fall-out shelters, or underneath stairs or sturdy furniture in the centre of the house. See Tornadoes and Lightning for more detailed shelter advice.

• Maintain an emergency pack containing food supplies, extra clothing, blankets, a first aid kit and medication, a battery-powered radio with fresh batteries, a flashlight, lantern, and tools for emergency repair jobs. Check them often and keep them together in your shelter area. Carry a similar pack in your vehicle.

• Preventive maintenance. Trim dead or rotting tree branches regularly, and remove dead trees to prevent them from toppling over during a storm.

• Choose a meeting place to make sure everyone in your family is safe and sound after a severe storm, in case you become separated during the storm.

• Maintain a full gas tank in your car, in case gas stations are forced to shut down in the aftermath of a severe storm.

• If you hear a severe thunderstorm watch for your area, meaning conditions are favourable for the development of severe thunderstorms:
  • Secure or put away loose objects such as outdoor furniture.
  • Put car in garage or carport if available.
  • Bring livestock to shelter.
  • Listen carefully for updated weather information. Remember that tornadoes are possible during a severe thunderstorm. Keep this in mind when making your preparations after hearing a severe thunderstorm watch.

• If you hear a severe thunderstorm warning, meaning that severe thunderstorms are highly probable or are occurring:
  • Keep calm.
  • Close all windows and doors if time permits.
  • Ensure children are indoors, or otherwise safely sheltered.
  • Go to your shelter and take along emergency pack.
  • If boating or swimming, head for land immediately and seek appropriate shelter.

• During a severe storm:
  • Stay away from all doors and windows if you are inside to avoid injury from broken or flying glass.
  • Don't travel. If caught in your car, open car windows slightly and park off the road away from tall objects and power lines. Set the brakes. Be wary of downed power lines and don't try to step outside the car if they are near or touching the car.
  • In the event of a tornado, abandon car and seek a sturdy shelter or low-lying area. See the Tornadoes section for further information.
  • If officials tell you to evacuate , do so. Follow their instructions. Take emergency pack, supplies, baby care items and personal documents and identification for each family member.
  • If caught outdoors, seek shelter in a low-lying area away from trees and free standing objects which may topple over or attract lightning. Be alert for flash floods if you seek shelter in a low lying area or ditch.

• After a severe storm:
  • Listen to radio for information. Follow instructions given by officials.
  • Provide first aid or get help for injured or trapped people.
  • Stay away from damaged buildings , dangling electrical wires or areas with possible gas leaks.
  • Watch for fire and be prepared to contact fire department.
  • Drive only if necessary. Leave the roads clear for emergency vehicles.
  • Use telephone only if necessary. Leave lines open for emergency use.
  • Check freezer and refrigerator for spoiled food if electricity has been off for a long time.
  • Purify drinking water by boiling, chlorinating, or adding purification tablets if contamination is suspected.