How to prepare for thunderstorms and to cope with them safely.


Thunderstorms can occur at any time of the year and just about anywhere in the world. Despite their small size in comparison to hurricanes and winter storms, all thunderstorms are dangerous. Every thunderstorm produces lightning. Other associated dangers of thunderstorms include tornadoes, strong winds, hail and flash flooding. Flash flooding is responsible for more fatalities than any other thunderstorm-associated hazard. See iJET's Advice Sheet on Flooding for more information.

Thunderstorms generally form in two ways; an air mass or approaching frontal systems. An air mass-generated thunderstorm is typically associated with a warm, moist air mass that is in place over a region; these storms usually occur in summer. Thunderstorms associated with approaching frontal systems are characteristically more severe than air mass type thunderstorms. Squall lines and tornadoes may be associated with this type of thunderstorm. See iJET's Advice Sheet on Tornadoes for more information.

Thunderstorms are sometimes accompanied by heavy rain, gusty winds, and hail. Under the right atmospheric conditions, thunderstorms can spawn tornadoes.

How to Prepare For Thunderstorms

Know the terms and facts regarding thunderstorms:

  • A Thunderstorm Warning tells you when and where severe thunderstorms are likely to occur.
  • A Thunderstorm Watch tells you when severe thunderstorm activity has been reported. Warnings indicate imminent danger to life and property to those in the path of the storm.
  • A thunderstorm is classified as severe if it produces hail at least three-quarters of an inch in diameter (1.9 cm), has winds of 58 mph (93 kph), or spurs a tornado.
  • Thunderstorms may occur singly, in clusters, or in lines, and typically produce heavy rain for a brief period (30 minutes to one hour).
  • When a thunderstorm approaches, secure objects outdoors that could blow away. Shutter windows, if possible, and secure outside doors. Use blinds, shades, or curtains if shutters are not available.

How to Cope With Lightning

The risk of lightning is perhaps the most common and deadly of what can occur with a thunderstorm. Lightning can be dangerous to people, animals, crops and property. In a thunderstorm, you will find lightning and thunder. The lightning present in all thunderstorms is an electrical discharge. Thunder is an explosion heard when atmospheric gases are suddenly heated by a discharge of lightning.

The unpredictability of lightning increases the risk to individuals and property, and can be reduced by following the following preventative steps:

  • When a thunderstorm threatens your area, move inside to a building or hardtop vehicle. Stay away from metallic objects; structures such as 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 chance to seek safe shelter, follow these recommendations:

  • In wooded areas, find a low area under a thick growth of small trees.
  • In open areas, find the lowest place nearby, such as a ravine, valley, or even a ditch, and crouch down. However, remain alert for flash flooding.
  • Do not remain near natural lightning rods, such as a tall, isolated tree. Do not stand on a hilltop, or open field. Also avoid isolated small structures in open fields.
  • Stay away from 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. Make yourself as small a target as possible by placing your hands over your ears and your head between your knees. Do not lie flat on the ground.

iJET Intelligent Risk Systems
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