Municipal Services

Additional Information

Additional Information For: Severe Storms, Tornadoes, Thunderstorms, Lightning, Hail, Heavy Rain, Floods

Severe Storms

If you are like many Canadians you may have cleaned up after a severe storm and you know the damage they can cause. Some problems cannot be prevented. High winds will topple trees and heavy rains will cause rivers to flood. But some damage can be avoided, or at least reduced, if you take a few simple precautions such as knowing the type of storms common to your area and what time of year they are likely to strike. Thunderstorms, tornadoes, hail, blizzards, high winds and heavy rain can develop quickly and hit hard, posing a threat to life and property. Storms such as tornadoes often strike too quickly to allow you to choose a shelter or to pack an emergency kit. You may want to have your family plan in place that outlines where you will go and how you will keep in touch with members of your family if a severe storm hits. Municipal, provincial and territorial emergency management organizations can provide valuable advice to help you prepare for emergencies.

  • Listen for the warnings: Environment Canada monitors the weather 24 hours a day, seven days a week. If a severe storm is on the horizon, the weather service issues watches, advisories and warnings through national, regional and local radio and television stations, as well as Environment Canada's Weather radio.
  • Weather watch: Conditions are favourable for a severe storm, even though one has not yet developed. This is usually issued early in the day. Keep monitoring weather conditions and listen for updated statements.
  • Weather warning: Severe weather is happening or hazardous weather is highly probable. If a weather warning is issued for a tornado, it means that one or more tornadoes have been observed or are forecast for the specified area. Other warnings include those for a severe thunderstorm, blizzard, high winds, heavy snow, snow squall, heavy rain and significant freezing rain. Be prepared.
  • Choose your shelter area: A basement, storm cellar or a closet beneath the stairs are good places to take shelter in the event of a severe storm. If none of these is available, sit underneath a sturdy piece of furniture on the ground floor in the centre of the building, away from the outside walls and windows. Be sure you discuss the shelter area with your family ahead of time.
  • When a severe storm is forecast. Severe weather can occur any time of the year, winter or summer. Make it a habit to listen to the local radio or television stations for severe weather warnings and advice. Make sure you have a battery-powered radio on hand; electricity frequently fails during a severe storm.
    • Secure everything that might be blown around or torn loose -- indoors and outdoors. Flying objects such as garbage cans and lawn furniture can injure people and damage property. If hail is forecast, you may want to protect your vehicle by putting it in the garage. (If the severe storm is upon you should not be trying to do these things.)
    • Never venture out in a boat. If you are on the water and you see bad weather approaching, head for shore immediately. Always check the marine forecast before leaving for a day of boating and listen to weather reports during your cruise.
    • If you are outdoors when a storm hits, take shelter immediately. If you are advised by officials to evacuate, do so. Take your emergency kit with you.
    • Stay calm. You will be better able to cope with emergencies.


Tornadoes form suddenly -- often proceeded by warm, humid weather -- and are always produced by thunderstorms, although not every thunderstorm produces a tornado.

Tornadoes are violent windstorms characterized by a twisting, funnel-shaped cloud, which forms at the base of cloudbanks and points towards the ground. Tornadoes usually move over the ground at anywhere from 20 to 90 kilometres per hour and often travel from the southwest to the northeast. They are erratic and can change course suddenly. It is not a good idea to chase tornadoes. 

Generally speaking, May to September is prime tornado months. Tornadoes usually hit in the afternoon and early evening but they have been known to strike at night too. Canada has several high-risk areas, including Alberta, southern Ontario, southern Quebec and a band of land which stretches from southern Saskatchewan and Manitoba through to Thunder Bay, Ontario. There are also tornado zones in the interior of British Columbia and in western New Brunswick.

There are warning signs, including:

  • severe thunderstorms, with frequent thunder and lightning
  • an extremely dark sky, sometimes highlighted by green or yellow clouds
  • a rumbling sound, such as a freight train might make, or a whistling sound, such as a jet aircraft might make
  • a funnel cloud at the rear base of a thundercloud, often behind a curtain of heavy rain or hail.

Things to do in case of a tornado:

  • If you live in one of Canada's high-risk areas, you should listen to your radio during severe thunderstorms. As a rule, when Environment Canada issues a tornado warning, radio stations broadcast it immediately. If you hear that a tornado warning has been issued for your area, take cover immediately.
  • If you are at home, go to the basement or take shelter in a small interior ground floor room such as a bathroom, closet or hallway. Failing that, protect yourself by taking shelter under a heavy table or desk. In all cases, stay away from windows, outside walls and doors.
  • If you are in an office or apartment building, take shelter in an inner hallway or room, ideally in the basement or on the ground floor. Do not use the elevator and stay away from windows. Avoid buildings such as gymnasiums, churches and auditoriums with wide-span roofs. These roofs do not have supports in the middle and may collapse if a tornado hits them. If you are in one of these buildings, take cover under a sturdy structure.
  • Do not get caught in a car or mobile home. More than 50 per cent of all deaths from tornadoes happen in mobile homes. Take shelter elsewhere -- such as a building with a strong foundation. If no shelter is available, lie down in a ditch away from the automobile or mobile home. However, beware of flooding from downpours and be prepared to move.
  • If you are driving and spot a tornado in the distance, try to get to a nearby shelter. If the tornado is close, get out of your car and take cover in a low-lying area. If a tornado seems to be standing still, then it is either travelling away from you or heading right for you.
  • In all cases, get as close to the ground as possible, protect your head and watch out for flying debris. Small objects such as sticks and straws can become lethal weapons when driven by a tornado's winds.


Thunderstorms develop in an unstable atmosphere when warm, moist air near the earth's surface rises quickly and cools. The moisture condenses to form rain droplets and dark thunderclouds called cumulonimbus clouds. These storms are often accompanied by hail, lightning, high winds, heavy rain and tornadoes. Thunderstorms are usually over in an hour, although a series of thunderstorms can last for several hours.


The air is charged with electricity during a thunderstorm. The most striking sign of this is 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, when actually the opposite is true. The main bolt is a whole series of lightning strikes, all taking the same path but at such a pace 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 meters. If you count fewer than 30 seconds, look around for shelter; if fewer than five seconds, take shelter urgently. Lightning is near and you do not want to be the tallest object in the area. It is recommended to wait 30 minutes after the last lightning strike in a severe storm before venturing outside again.

During a severe lighting storm:

  • If you are in a building:
    • Stay there, but away from windows, doors, fireplaces, radiators, stoves, sinks, bathtubs, appliances, metal pipes, telephones and other materials which conduct electricity.
    • Unplug TVs, radios, toasters and other electrical appliances.
    • Do not go out to rescue the laundry on the clothesline, as it conducts electricity.
    • Don't use the phone or other electrical equipment.(You can use a cellular telephone.)
  • If you are outside:
    • Seek shelter in a building, cave or in a depressed area such as a ditch or a culvert, but never under a tree.
    • If you're caught in the open, crouch down with your feet close together and your head down (the "leapfrog" position).
    • Don't lie flat -- by minimizing your contact with the ground, you reduce the risk of being electrocuted by a ground charge.
    • Keep away from telephone and power lines, fences, trees and hilltops.
    • Get off bicycles, motorcycles, tractors, and golf carts -- and don't use metal shovels and golf clubs -- as they conduct electricity.
  • If you are in a car, stay there but pull away from trees where heavy branches might fall on you.


Hail forms when updrafts in thunderclouds carry raindrops upwards into extremely cold areas of the atmosphere. The raindrops freeze and are bounced around in the powerful winds within thunderclouds while new layers of ice are added. Eventually, the hailstones grow too heavy to be supported by the updrafts and fall to the ground. Some hailstones are the size of peas while others can be as big as grapefruits.

Take cover when hail begins to fall. Do not go out to cover plants, cars or garden furniture or to rescue animals. Hail comes down at great speed, especially when accompanied by high winds. Although no one in Canada has ever been killed by hail, people have been seriously injured by it.

Heavy Rain

A heavy rainfall can result in flooding. This is particularly true when the ground is still frozen or already saturated from previous storms. Floods may also result if a heavy rain coincides with the spring thaw.

If you know there is flooding or the possibility of flooding in your area, keep your radio on to find out what areas are flooded, what areas are likely to be flooded, as well as what roads are safe, where to go and what to do if the local emergency team asks you to leave your home.

Generally speaking, it is a good idea to avoid driving through flooded roads and underpasses. The water may be a great deal deeper than it looks and you could get stuck. You may also want to avoid crossing bridges if the water is high and flowing quickly.


  • Turn off basement furnaces and the outside gas valve.
  • Shut off the electricity. If the area around the fuse box or circuit breaker is wet, stand on a dry board and shut off the power with a dry wooden stick.
  • Never try to cross a flooded area on foot. The fast water could sweep you away.
  • If you are in a car. Try not to drive through floodwaters. Fast water could sweep your car away. However, if you are caught in fast-rising waters and your car stalls, leave it, and save yourself and your passengers.

Things To Do After A Storm:

  • Listen to your radio for information and follow instructions.
  • Give first aid to people who are injured or trapped. Get help, if necessary.
  • Unless you are asked to help or are qualified to give assistance, please stay away from damaged areas.
  • Do not go near loose or dangling power lines. Report them and any broken sewer and water mains to the authorities.
  • Lightning and downed power lines can cause fires. Report fires to the fire department. Know how to fight small fires.
  • Water supplies may be contaminated, so purify your water by boiling it for 10 minutes, by adding water-purification tablets or by adding one drop of unscented chlorine bleach to one litre of water (or three drops for cloudy water). If you use chlorine bleach to purify the water, stir the bleach in and wait 30 minutes before drinking. The water should have a slight chlorine smell.
  • Please leave the telephone lines free for official use. Do not use the telephone except in real emergencies.
  • Drive cautiously and only if necessary. Debris, broken power lines and washed-out or icy roads and bridges will make driving dangerous after a severe storm. Please give way to emergency vehicles at all times.
  • If the power has been off for several hours, check the food in the refrigerator and freezer in case it has spoiled.

Information for these pages was taken from the Public Safety and Emergency Preparedness Canada web site with permission.