Extreme Thunder, Lightning & Hail

What Causes Thunderstorms?

Thunderstorms are caused by strong rising air currents and are most likely to develop when weather is hot, humid, and hazy. Cooler air coming from the higher elevation hits the warmer air rising from the ground, which creates an unstable air mass. Thunderstorms are most common in June, July and August, but, can occur any month of the year.

What Are the Dangers?

Strong winds, hail and tornadoes are dangers associated with some thunderstorms. Damage from these winds can equal the damage of most tornadoes. Heavy rain from thunderstorms can also lead to flash flooding.

How Do I Know a Thunderstorm is Coming?

A “severe weather watch” from Environment Canada indicates that conditions favour the occurrence of a certain type of hazardous weather. Monitor weather conditions through a local media station or website, and take appropriate precautions.

A “severe weather warning” issued by Environment Canada indicates that a hazardous event is imminent in about 30-60 minutes. You should seek shelter indoors and continue to monitor weather conditions.

How to Prepare

  • Review Before an Emergency for general information on how to prepare.
  • Build or restock your Emergency Preparedness Kit.
  • Go to a safe place! This should be a place without windows or glass doors. If a sturdy building is not nearby, get into a hard-topped metal vehicle and close the windows. Stay inside until 30 minutes after the last rumble of thunder. Review the Severe Storm Preparation Guide (PDF).
  • Check local forecasts and consider the conditions, especially if you are planning to be outside.
  • If thunder storms are forecasted, have your Emergency Kit ready and ensure your flashlight is working properly. Power outages are common in these types of storms.
  • Do not collect the laundry on the clothesline because it may 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.
  • 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.
  • Secure outdoor objects that could blow away or cause damage.
  • Familiarize yourself with these terms to help identify a thunderstorm hazard.

During a Thunderstorm

The Lower Mainland is prone to thunderstorms, and all thunderstorms have the potential to be dangerous. Every thunderstorm produces lightning, which injures more than 150 people in Canada every year. Thunder storms are characterized by the bright flash of lightning and rumble of thunder. Although beautiful in many ways, thunder storms can be dangerous, especially if you are outside.
  • No place outside is safe when a thunderstorm is in the area.
  • If you hear thunder, lightning is close enough to strike you – get inside immediately.
  • When inside, stay away from windows, plumbing, metal fixtures such as sinks and doorways.
  • Stay off land line phones. Cellular phones are ok to use as long as they are not plugged into charge.
  • If you are outside and unable to find shelter get to low ground as quickly as possible.
  • Never lie flat on the ground or take shelter beneath a tree, or rocky overhang.
  • Stay away from water and other tall objects such as light poles and power lines.
  • Crouch low to ground with your feet together and head tucked into your body.
  • Monitor the local media and have flashlights on hand in case the power goes out.

After the Thunderstorm

  • Be sure that the storm has left the area before going outside. It is best to wait 30 minutes after you last hear thunder.
  • Restock any emergency supplies.
  • If lightning strikes you or someone you know, call 9-1-1 for medical assistance as soon as possible. The following are things you should check when you attempt to give aid to a victim of lightning:
    • Breathing: if breathing has stopped, begin mouth-to-mouth resuscitation
    • Heartbeat: if the heart has stopped, administer CPR
    • Pulse: if the victim has a pulse and is breathing, look for other possible injuries. Check for burns where the lightning entered and left the body. Also be alert for nervous system damage, broken bones and loss of hearing and eyesight
  • Never drive through a flooded roadway. Turn around, don’t drown!
  • Stay away from storm-damaged areas to keep from putting yourself at risk from the effects of severe thunderstorms.
  • Continue to listen to the Weather Radio or to local radio and television stations for updated information or instructions, as access to roads or some parts of the community may be blocked.
  • Help people who may require special assistance, such as infants, children and the elderly or those with access or functional needs.
  • Stay away from downed power lines and report them immediately.
  • Watch your animals closely. Keep them under your direct control.