A severe thunderstorm is often accompanied by torrential rain, hail, lightning or high winds. It can cause significant damage, such as flooding, fires, power failures, electrocution, and sometimes tornados.
A thunderstorm involves lightning and thunder. It generally lasts no more than one hour, but a series of thunderstorms can last several hours.
How to prepare when severe thunderstorms are forecast?
Follow weather alerts for your region.
Postpone all unnecessary travel.
To find out the distance separating you from the thunderstorm, count the seconds between the flash of lightning and the thunderclap. One second represents approximately 300 metres. For example, if five seconds elapse between the lightning and the thunder, the thunderstorm is about 1500 m (1.5 km) from where you are. You must take shelter if the thunderstorm is less than 10 km away.
When indoors :
- Disconnect electrical devices if your safety is not compromised.
- Stay away from doors and windows. Find shelter in a room at the centre of the building, as lightning can go through outside walls, windows and doors.
- Stay away from objects that conduct electricity, such as household appliances, sinks, bathtubs, radiators and metal pipes.
- Do not use televisions or computers because they can be seriously damaged by lightning surge. Use battery-operated devices instead.
- Avoid using phones connected to landlines because lightning travels along electrical wiring and cords. Use wireless or cell phones instead.
- Wait about 30 minutes after the last rumble of thunder before going outside.
When in a vehicle :
- Avoid driving during the thunderstorm.
- Stay away from power lines. If a power line falls on your vehicle, remain inside the vehicle and wait for help.
A vehicle with a hard-topped roof (not a convertible) can serve as shelter and protect you from lightning.
When outdoors :
- Stay away from trees, telephone poles, power lines, objects that conduct electricity (e.g., motorcycles, lawnmowers, golf clubs or umbrellas), water and any elevated place in an open area.
- Seek shelter in the lowest area that you can find, for example a ditch.
- If you are in the woods, seek shelter under a thick growth of small trees or bushes.
- Squat down, put your head on 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 in a boat, head for shore immediately.
Follow the evolution of the situation and respect instructions issued by official sources of information (e.g., your municipality, the Gouvernement du Québec).
Act safely if a person is struck by lightning
If a person near you is struck by lightning, call 911 or go to the nearest hospital centre. Be aware that:
- 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.
Direct consequences of being struck by lightning are skin burns, heart and hearing problems, as well as visual and nervous problems.
What to do after
Make sure that your home is safe.
Check the damage sustained and the debris left by the thunderstorm.
Pick up the debris. Watch out for sharp material such as sheet metal or glass.
Pay attention to stress reactions after a disaster:
- Apathy or loss of energy
- Increased alcohol or drug use
Appropriate psychological guidance can help you cope with responsibilities stemming from the situation. Contact Info-Santé at 811 and select Info-Social to speak with a social worker. This confidential service is available 24 hours a day, 7 days a week.
Last update: September 2, 2021