How to prepare for thunderstorms and cope with them safely.
Thunderstorms can occur at any time of the year and throughout the world. Thunderstorms are dangerous despite their small size due to the production of lightning. Thunderstorms can also contain strong winds, hail, flooding downpours, and tornadoes.
Thunderstorms form due to instability in the atmosphere. This typically occurs when moisture-laden air masses are heated by the sun, or if a frontal system interacts with an unstable air mass. Thunderstorms that develop ahead of a frontal system are generally stronger than those associated with daytime heating. Squall lines and tornadoes may be associated with this type of thunderstorm. See iJET's Advice Sheet on Tornadoes for more information.
How to Prepare For Thunderstorms
Know the terms and facts regarding thunderstorms:
- A Severe Thunderstorm Watch is issued when atmospheric conditions are favorable for severe thunderstorms to develop.
- A Severe Thunderstorm Warning is issued when radar or trained spotters have identified severe thunderstorm characteristics; warnings indicate imminent danger to both life and property in the area with the path of the storm.
- Thunderstorms are classified as severe when they produce a tornado, wind gusts of 58 mph (93 kph) or greater, and/or hailstones at least one inch (2.5 cm) in diameter.
- When a thunderstorm approaches, ensure that all loose objects are secured. If possible, protect windows with shutters. Avoid windows and glass doors during the storm to mitigate the threat of lightning.
How to Mitigate the Threat of Lightning
During a thunderstorm, people, animals, crops, and property are exposed to the dangers of lightning. When the atmosphere is quickly heated by lightning, thunder is produced. If you can hear thunder, you are close enough to be struck by lightning. Seek shelter immediately.
To reduce the threat of lightning, take the following steps:
- When a thunderstorm threatens your area, seek shelter in a building or hardtop vehicle. Avoid metallic objects; plumbing and bathroom fixtures can conduct electricity.
- Unplug appliances and other valuable electrical items such as computers, since power surges from lightning strikes can cause damage.
- Monitor local media on a battery-operated radio for updates on storm activity.
If caught outside with no opportunity to seek safe shelter, follow these recommendations:
- Find a low area, such as a ravine, gully, valley, or ditch, and crouch down. However, remain alert for flash flooding.
- Avoid natural lightning rods, such as a tall, isolated tree in a field. Avoid open fields and elevated areas such as hilltops.
- Avoid area of open water. If you are caught boating or swimming, proceed to land immediately, and seek shelter.
- If you feel your hair stand on end (which indicates that lightning is about to strike), squat low to the ground on the balls of your feet to minimize your contact with the ground. Do not lie flat on the ground. Make yourself as small a target as possible by placing your hands on your knees.
- Related Advice:
What to do before, during and after a flood.
- Related Advice:
How to prepare for a hurricane/tropical cyclone/typhoon.