Thunderstorms, lightning and hail

Thunderstorms, Lightning and hail

Thunderstorms are often accompanied by high winds, hail, lightning, heavy rain and in rare cases can produce tornadoes.
Hail is formed when updrafts in thunderclouds carry raindrops upward into extremely cold areas of the atmosphere, where they freeze and merge into lumps of ice.

Thunderstorms and lightning occur throughout Canada but less frequently in the North. On average, 10 people die each year in Canada and up to 160 are injured during such storms. Thunderstorms are usually over within an hour, although a series of thunderstorms can last several hours.  

Hailstorms occur across Canada, mostly from May to October. They are most frequent in Alberta, the southern Prairies and in southern Ontario.     

Some hailstones are the size of peas while others can be as big as grapefruits. Hail comes down at great speed, especially when accompanied by high winds and can cause serious injuries and damages.

What to do

•           Before a severe thunderstorm, unplug radios, televisions and appliances (especially those that may start up automatically when the power is restored). Listen for weather updates on your wind-up or battery-powered radio.

•           If possible, avoid using a corded phone during a thunderstorm. Stay away from items that conduct electricity, such as telephones, appliances, sinks, bathtubs, radiators and metal pipes. These items may conduct electricity.

•           Similarly, do not ride bicycles, motorcycles, tractors, golf carts or use metal shovels or golf clubs.

•           Do not collect the laundry on the clothesline because it may conduct electricity.

•           Take shelter immediately, preferably in a building but, failing this, in a depressed area such as a ditch. Never go under a tree as roots extending from the tree can conduct electricity.

•           To estimate how far away the lightning is, count the seconds between the flash of lightning and the thunderclap. Each second represents over 300 metres. If you count fewer than 30 seconds, take shelter.

•           Wait 30 minutes after the last lightning strike before venturing outside again.

•           Consult the Government of Canada/Power Outages — What to do?” booklet for more information.

•           If hail is forecast, protect your vehicle by putting it in the garage or other enclosed space.

•           Take cover when hail begins to fall. Do not go out to cover plants, cars or garden furniture.

•           When a hailstorm hits, stay indoors, and keep yourself and your pets away from windows, glass doors and skylights which can shatter if hit by hailstones.

If outdoors

•           If you are caught in the open in a severe storm, do not lie flat. Crouch down with your feet close together and your head down (the “leap-frog” position).

•           Seek shelter if possible, like a comfort station in campgrounds. A hard top vehicle will provide the next best shelter, but do not touch any metal surfaces during a thunderstorm.

•           If shelter is not available, look for low lying areas but stay away from streams in the event of flash flooding.

•           The key to severe storms in summer is to minimize your contact with the ground and make yourself a smaller target. This reduces the risk of being electrocuted by a ground charge.

Tornadoes

Tornadoes are rotating columns of high winds. Canada gets more tornadoes than any other country with the exception of the United States, averaging about 50 tornadoes per year.

•           Can move quickly (up to 70 km/hour) and leave a long path of destruction (at other times the tornado can be small with rapidly fluctuating wind speeds).

•           Can uproot trees, overturn cars and demolish houses.

•           Usually hit in the afternoon and early evening, but have been known to strike at night.

•           Are relatively common in Canada, but only in specific regions: Alberta, Manitoba, Saskatchewan, Ontario, Quebec, New Brunswick, and the interior of British Columbia.

•           Have a season extending from April to September with peak months in June and July, but can occur at any time of year.

Warning signs of a potential tornado

•           Severe thunderstorms.

•           An extremely dark sky, sometimes highlighted by green

or yellow clouds.

•           A rumbling or a whistling sound caused by flying debris.

•           A funnel cloud at the rear base of a thundercloud, often behind a curtain of heavy rain or hail.

What to do

In all cases

•           Get as close to the ground as possible, protect your head and watch for flying debris.

•           Do not chase tornadoes — they are unpredictable and can change course abruptly.

•           A tornado is deceptive. It may appear to be standing still but may in fact be moving toward you.

In a house

•           Go to the basement or take shelter in a small interior ground floor room such as a bathroom, closet or hallway.

•           If you have no basement, protect yourself by taking shelter under a heavy table or desk.

•           In all cases, stay away from windows, outside walls and doors.

On a farm

•           If your personal safety is not at risk, you may have time to open routes of escape for your livestock. Open the gate, if necessary, and then exit the area in a direction perpendicular to the expected path of the tornado.

In a recreational vehicle or mobile home

•           Find shelter elsewhere, preferably in a building with a strong foundation.

•           If no shelter is available, crouch down in a ditch away from the mobile home or recreational vehicle. Beware of flooding from downpours and be prepared to move.

In a high rise building

•           Take shelter in an inner hallway or room, ideally in the basement or on the ground floor.

•           Do not use the elevator.

•           Stay away from windows.

In a gymnasium, church or auditorium

•           Large buildings with wide-span roofs may collapse if a tornado hits.

•           If you are in one of these buildings and cannot leave, take cover under a sturdy structure such as a table or desk.

In a vehicle

•           If you spot a tornado in the distance go to the nearest solid shelter.

•           If the tornado is close, get out of your car and take cover in a low-lying area, such as a ditch.

•           Do not take shelter under an overpass or a bridge. Winds can accelerate under an overpass or a bridge and cause injury or death from flying debris.

Thanks to the Government of Canada/Severe Storms Bulletin

Posted June 12