All thunderstorms contain lightning. When the build up of positive and negative charges within a thunderstorm becomes strong enough, lightning appears as a "bolt." This flash of light usually occurs from the clouds or between the clouds and the ground. A bolt of lightning reaches a temperature approaching 50,000E F in a split second. The rapid heating and cooling of air near the lightning causes thunder.

To estimate the number of miles you are from a thunderstorm, count the number of seconds between the flash of lightning and the next clap of thunder. Divide this number by five. You are in danger from lightning if you can hear thunder. Knowing how far away a storm is does not mean that you’re in danger only when the storm is overhead.

Warning signs of a thunderstorm:

• Dark, towering, or threatening clouds 
• Flashes of lightning
• Sound of thunder 
• Static on your AM radio 

• Secure outdoor objects such as lawn furniture that could blow away or cause damage or injury. Take light objects inside.
• Shutter windows securely and brace outside doors. 
• Tune in your battery operated radio for storm information.
• Make sure you are in a sturdy shelter. Do not take shelter in small sheds, under isolated trees or in convertible automobiles. If lightning is occurring and a sturdy shelter is not available, get inside a hard top automobile and keep the windows up.
• Get out of boats and away from water.
• Telephone lines and metal pipes can conduct electricity. Unplug appliances not necessary for obtaining weather information. Avoid using the telephone or any electrical appliances. Use phones ONLY in emergency.
• Do not take a bath or shower.
• Turn off air conditioners. Power surges from lightning can overload the compressors.
• Get to higher ground if flash flooding or flooding is possible. 

• Find a low spot away from trees, fences and poles. Make sure the place you pick is not subject to flooding. Avoid tall structures such as towers, tall trees, fences, telephone or power lines.
• If you are in the woods, take shelter under shorter trees.
• If you feel your skin tingle or your hair stand on end, an indication lightning is going to strike, squat low to the ground on the balls of your feet. Place your hands on your knees with your head between them. Make yourself the smallest target possible, and minimize your contact with the ground.
• Stay away from natural lightning rods such as golf clubs, tractors, fishing rods, bicycles or camping equipment.
• If you are boating or swimming, get to land and find shelter immediately.

• Pull safely onto the shoulder of the road away from any trees that could fall on the vehicle.
• Stay in the car and turn on emergency flashers until the heavy rains subside.
• Avoid flooded roadways.

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