A severe thunderstorm can involve the following phenomena :
- torrential rains;
- frequent lightning and thunder;
- winds in excess of 90 km/h.
During a thunderstorm, a flash of lightning can produce an electrical discharge of more than 30 million volts.
The strong winds that accompany a severe thunderstorm can cause serious damage. The thunderstorm itself can cause flooding, fires, power failures and electrocution, among others.
You can limit the dangers during a severe thunderstorm :
Find out about weather alerts in effect in your region or the area where you are going. Take those alerts into account when planning your activities and travel.
Knowing the distance between you and the thunderstorm can help you to protect yourself from lightning. Count the seconds between the flash of lightning and the thunderclap. One second represents approximately 300 metres. If you count 30 seconds or less, you must take shelter immediately.
The safest action is to take shelter as soon as you hear any thunder.
Follow the safety rules wherever you may be. In the case of severe thunderstorms forecast, follow the instructions provided by the authorities.
To stay safe when indoors, do as follows :
- disconnect electrical devices;
- close doors and windows securely;
- find shelter in a room at the centre of the building, as lightning can go through outside walls, windows and doors;
- stay away from pipes and objects that conduct electricity, such as cooking stoves and showers;
- do not use the television or the computer;
- use battery-powered devices, if possible;
- make calls using a wireless phone or a cell phone if you have one; otherwise, use your stationary phone strictly for emergencies;
- wait for the calm to return before leaving your shelter.
In a vehicle
A vehicle with a hard-topped roof (not a convertible) can serve as shelter and protect you from lightning. It is preferable not to drive during the thunderstorm and to stay far away from power lines. If a power line falls on your vehicle, remain inside the vehicle and wait for help.
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If you are outdoors during a thunderstorm, there are no safe shelters. The following advice will help decrease the risks related to lightning :
- seek shelter in the lowest area that you can find, for example a ditch;
- squat down;
- put your head against your knees and cover it with your arms;
- if possible, put insulating material such as a plastic bag between the ground and yourself;
- be ready to move in the event of flash flooding.
If you are with others, keep everyone at least three metres apart, as lightning can travel between people.
Stay away from :
- telephone poles;
- power lines;
- objects that conduct electricity, such as motorcycles, lawnmowers, golf clubs or umbrellas;
- hills or any elevated places in a open area.
If you are in the woods, seek shelter under a thick growth of small trees or bushes.
If you are in a boat, head for shore immediately.
Avoid barns with a sheet-metal roof that is supported by wooden beams. In addition, avoid open constructions, such as bus shelters.
If a person near you is struck by lightning, it is a medical emergency. Call 911 or go to the closest hospital centre. Be aware that :
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- you can touch or transport the person to a safe location without any danger, as he or she does not carry an electrical charge;
- you can administer artificial respiration or CPR until help arrives;
- anyone who is struck by lightning must consult a physician, even if there is no apparent injury and the person feels well.
If your home was damaged, you must inform :
- your fire department to verify that you can enter your home;
- your insurer;
- the financial institution that gave you a mortgage.
Below is advice to follow when you return to your home once you have obtained confirmation that it is safe :
- restore electricity, heating and water, unless the equipment is damaged;
- dry out the premises and clean the home;
- determine which personal items must be cleaned by experts;
- make sure that water, food and medications are fit for consumption.
Other recommendations apply if your home was damaged by a flood.
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