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Severe Thunderstorm

Thunderstorms occur frequently during the afternoon and evening hours of Florida's hot, humid spring and summer months, but they can occur year-round and they are always dangerous.  Thunderstorms may occur singly, in clusters, or in lines, and typically produce very heavy rain for a relatively brief period, anywhere from 30 minutes to an hour. 

All thunderstorms have lightning, and the often torrential rain associated with a thunderstorm can cause rapid flooding in low-lying areas;  but these systems are classified as severe thunderstorms by the National Weather Service when they include the potential for one or more of the following: 

  • hail one inch or greater in diameter,

  • wind gusts in excess of 57.5 mph, or

  • a tornado.


Click HERE for the FEMA
Ready Business Severe Wind Toolkit

FEMA graphic indicating traits of severe thunderstorms, a powerful wind icon, cloud with lighting and hail icon, a flash flood and tornado icon
Graphic heading says Prepare Now in a Blue Circle
Graphic heading says Survive During the Hazard in Orange Circle
Graphic heading says Be Safe After the Hazard in Green Circle




  • Keep your home "storm-ready."  Trim trees and branches near your house.  Ideally, no part of a tree should touch your home, and branches that hang over your roofline should be cut regularly.

  • Check the forecast regularly to see if you're at risk for severe weather.  Listen to local news or a NOAA Weather Radio to stay informed about severe thunderstorm watches (when the conditions are right for one to form) and warnings (when they are imminent or occurring in the area.)  

  • Sign up for Severe Thunderstorm Warnings through the AlertNassau notification system.

  • Pick a safe room in your home as your storm shelter - an interior room (with no windows) on the lowest floor where people and pets can go when severe thunderstorm warnings are issued.  A bathroom or closet can protect you from flying debris.

  • If you have time before severe weather hits, secure loose objects, close windows and doors, and move any valuable objects inside or under a sturdy structure.

  • Encourage your loved ones and neighbors to prepare for severe thunderstorms. 

  • Take free CPR training from the Medical Reserve Corps so you can help if someone is hurt during severe weather.

  • If you have time before the severe weather hits, secure loose objects, close windows and doors, and move any valuable objects inside or under a sturdy structure.

  • Continue to listen to local news or a NOAA Weather Radio to stay updated.

  • When a Severe Thunderstorm Warning is issued, damaging wind or large hail are approaching, Shelter-In-Place:  

    • At Home - Go to an interior room (with no windows) on the lowest floor.  Take your pets with you.

    • At Work or School - Stay away from windows.  Do not go to large open rooms such as cafeterias, gymnasiums or auditoriums.  

    • Outside - Go inside a sturdy, site-built structure immediately.  Sheds and storage facilities are not safe.  Taking shelter under a tree can be deadly - it puts you at a greater risk of getting struck by lightning and the tree, or heavy branches, may fall.

    • In a Vehicle - Being in a vehicle during severe thunderstorms is safer than being outside; however, drive to the closest secure shelter if there is sufficient time.

  • Continue listening to local news or a NOAA Weather Radio to stay informed - more severe thunderstorms could be headed your way.

  • Let your family and close friends know that you're okay.  Text messages are  more reliable than phone calls.

  • After the severe weather threat has ended, check your property for damage.  Stay out of damaged buildings.  Wear long pants, a long-sleeved shirt and sturdy shoes to walk through damage and debris.  Don't let pets walk around in debris.

  • Contact local authorities if you see power lines down. 

  • If your home is damaged, take photographs and contact your insurance agent.  Beware of people who drive up and offer to repair your property.

  • Check on your neighbors.  If you come across someone who is injured, provide first aid (if you are trained and able) and call 9-1-1 to alert emergency responders.

Image with helpful tips on keeping your home storm ready
Storm-Ready Home

Keep Your Home "Storm-Ready"

National Weather Service Graphic describing Watch versus Warning.  A Thunderstorm Watch issued when a severe thunderstorm is possible, be prepared!  A Thunderstorm Warning is issued when one is happening nearby, take shelter immediately!
Image of tips for preparing a manufactured home before a storm: check tie-down anchoring, secure items around the home, turn off water and fuel lines, evacuate - it is never safe to remain in a mobile home during a severe thunderstorm or hurricane that might spawn a tornado.
Indoors during thunderstorm.jpg
Graphic illustrating safe behavior after a storm; stay inside until it has passed, be aware of downed power lines, keep away from flood water, only run generators more than 20 feet from the home.
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