Thunderstorms affect relatively small areas, compared with most other storms. The typical thunderstorm is 15 miles in diameter and lasts for 30 minutes — but whatever their size, all thunderstorms are dangerous.
Severe thunderstorms produce large hail or winds of at least 58 mph. Some wind gusts can exceed 100 mph and produce tornado-like damage. That’s why many communities will sound their outdoor sirens for damaging straight-line winds.
When a severe thunderstorm threatens, stay inside a strong structure. Mobile home occupants should go to a more permanent structure.
Thunderstorm Winds
Thunderstorms can produce straight-line winds that exceed 100 miles per hour. For this reason you should treat severe thunderstorms just as you would tornadoes. Move to an appropriate shelter if you are in the path of the storm.
The strong rush of wind from a thunderstorm is called a downburst. The primary cause is rain-cooled air that accelerates downward, producing potentially damaging gusts of wind.
Strong downbursts can be mistaken for tornadoes, and they’re often accompanied by a roaring sound similar to that of a tornado. Downbursts can easily overturn mobile homes, tear roofs off houses and topple trees. Campers are especially vulnerable because trees can fall into campsites and onto tents.
Minnesota’s strongest thunderstorm gust was 85 mph on June 19, 2007, near Goodridge .
Hail
Hail is product of thunderstorms that causes nearly $1 billion in damage every year. Most hail is about pea-sized. Much of it is the size of baseballs, and it can reach grapefruit-size. Large hail stones fall faster than 100 mph and have been known to kill people.
Lightning
Every thunderstorm produces lightning!
Lightning kills about 100 Americans each year — more than tornadoes — and causes about 300 injuries.
Lightning Safety Tips
- NO PLACE outside is safe when thunderstorms are in the area!
- If you hear thunder, lightning is close enough to strike you.
- When you hear thunder, immediately move to safe shelter: a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up.
- Stay in safe shelter at least 30 minutes after you hear the last sound of thunder.
Indoor Lightning Safety
- Stay off corded phones, computers and other electrical equipment that put you in direct contact with electricity.
- Avoid plumbing, including sinks, baths and faucets.
- Stay away from windows and doors, and stay off porches.
- Do not lie on concrete floors, and do not lean against concrete walls.
Last Resort Outdoor Risk Reduction Tips
If you are caught outside with no safe shelter anywhere nearby the following actions may reduce your risk:
- Immediately get off elevated areas such as hills, mountain ridges or peaks
- Never lie flat on the ground
- Never shelter under an isolated tree
- Never use a cliff or rocky overhang for shelter
- Immediately get out and away from ponds, lakes and other bodies of water
- Stay away from objects that conduct electricity (barbed wire fences, power lines, windmills, etc.)
Myths and Facts About Lightning
Myth: If it is not raining, there is no danger from lightning.
Fact: Lightning often strikes away from rainfall. It may occur as far as ten miles away from any rainfall.
Myth: Rubber soles on shoes or rubber tires on a car will protect you from being injured by lightning.
Fact: Rubber provides no protection from lightning. However, the steel frame of a hard-topped vehicle provides some protection if you are not touching metal.
Myth: People struck by lightning carry an electrical charge and should not be touched.
Fact: Lightning victims carry no electrical charge and should be attended to immediately.
Myth: Heat lightning occurs on very hot summer days and poses no threat.
Fact: What is referred to as heat lightning is actually lightning from a thunderstorm too far away for thunder to be heard. However, the storm may be moving in your direction.
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