A thunderstorm is considered severe if it produces hail at least 1 inch in diameter or has wind gusts of at least 58 miles per hour. Every thunderstorm produces lightning, which kills more people each year than tornadoes or hurricanes. Heavy rain from thunderstorms can cause flash flooding and high winds can damage homes and blow down trees and utility poles, causing widespread power outages.

Here’s what the American Red Cross and other experts say you should do:
Listen to local news or NOAA Weather Radio for emergency updates.Watch for signs of a storm, like darkening skies, lightning flashes or increasing wind.
Postpone outdoor activities if thunderstorms are likely to occur.
Many people struck by lightning are not in the area where rain is occurring.
If a severe thunderstorm warning is issued, take shelter in a substantial building or in a vehicle with the windows closed. Get out of mobile homes that can blow over in high winds.
If you can hear thunder, you are close enough to be in danger from lightning.The National Weather Service recommends staying inside for at least 30 minutes after the last thunder clap.
Avoid electrical equipment and telephones. Use battery-powered TVs and radios and cordless phones or cell phones instead.
Close outside doors securely. Keep away from windows.
Do not take a bath, shower or use plumbing.
If you are driving, try to safely exit the roadway and park. Stay in the vehicle and turn on the emergency flashers until the heavy rain ends. Avoid touching metal or other surfaces that conduct electricity in and outside the vehicle.
If you are outside and cannot reach a safe building, avoid high ground; water; tall, isolated trees; and metal objects such as fences or bleachers.

Glossary
SEVERE THUNDERSTORM WATCH — Severe thunderstorms are possible in and near the watch area.
SEVERE THUNDERSTORM WARNING — Severe weather has been reported by spotters or indicated by radar.
Warnings indicate imminent danger to life and property.

A few words about LIGHTNING

Storms do not have to qualify as “severe” or be right overhead to bring dangerous lighting to an area. According to the Florida Division of Emergency Management, all thunderstorms contain lightning, and lightning can strike 10 miles or more from where it is raining, seeming to come “from a clear blue sky.”

The division’s website recommends the 30/30 rule: Go indoors if, after seeing lightning, you cannot count to 30 seconds before hearing thunder and stay indoors for 30 minutes after hearing the last thunder clap.