Severe Thunderstorm

All thunderstorms can be dangerous, and some have the potential to become severe.

Thunderstorms can produce hazards such as lightning, hail, straight-line winds, flash flooding, and tornadoes.

Severe Thunderstorm Watch:

A Severe Thunderstorm Watch is issued when environmental conditions are right to produce severe thunderstorms in and around the watch area. This does not guarantee that severe thunderstorms will form, but individuals within the watch area should take action to ensure they are prepared for storms. This may include creating contingency plans for outdoor events or ensuring all individuals in your workplace or residence hall understand the dangers of severe thunderstorms.

Severe Thunderstorm Warning:

A Severe Thunderstorms Warning means a severe thunderstorm has been sighted or indicated by radar. A thunderstorm may be defined as "severe" if it meets one or more of the following criteria:

  • It contains winds of 58 mph or faster
  • It contains hail that is 1-inch diameter or larger


Lightning is a hazard with all storms. Lightning continues to be one of the top three storm-related killers in the United States. On average, lightning kills 51 people per year in the US, and injures hundreds more. Although most lightning victims survive, people struck by lightning often report a variety of long-term, debilitating symptoms.

If thunderstorms and lightning are occurring in your area, you should:

  • Use your battery-operated NOAA Weather Radio for updates from local officials.
  • Avoid contact with corded phones and devices including those plugged into electric for recharging. Cordless and wireless phones not connected to wall outlets are OK to use.
  • Avoid contact with electrical equipment or cords. Unplug appliances and other electrical items such as computers and turn off air conditioners. Power surges from lightning can cause serious damage
  • Avoid contact with plumbing. Do not wash your hands, do not take a shower, do not wash dishes, and do not do laundry. Plumbing and bathroom fixtures can conduct electricity.
  • Stay away from windows and doors and stay off porches.
  • Do not lie on concrete floors and do not lean against concrete walls.
  • Avoid natural lightning rods such as a tall, isolated tree in an open area.
  • Avoid hilltops, open fields, the beach or a boat on the water.
  • Take shelter in a sturdy building. Avoid small structures in open areas.
  • Avoid contact with anything metal –motorcycles, golf carts, golf clubs, and bicycles.
  • 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.


  • Hail are hard, frozen nuggets formed when raindrops pass through a belt of cold air on their way to earth. The cold air causes the raindrops to freeze into small blocks of ice. Hail most commonly causes damage to property and vehicles. Considering the fact that large stones can fall at speeds faster than 100 mph. Stay away from windows and glass doors. Turn on a radio, weather alert radio, or television for current information about the weather.

Straight Line Winds

Damaging winds are often called “straight-line” winds to differentiate the damage they cause from tornado damage. Strong thunderstorm winds can come from a number of different processes. Most thunderstorm winds that cause damage at the ground are a result of outflow generated by a thunderstorm downdraft. Damaging winds are classified as those exceeding 50-60 mph.

Inside of a building:

  • Move to the lowest floor and stay away from windows.
  • Taking shelter in a basement is strongly encouraged, especially if you are surrounded by trees that could fall onto the building.

In a mobile home or manufactured home:

  • Move to a stronger building if one is nearby
  • Mobile and manufactured homes can usually withstand low-end straight-line windstorms, but as winds reach or exceed 70 mph, the risk of these homes being blown apart or struck by falling trees increases greatly


  • Keep both hands on the wheel and slow down.
  • Pull over to the shoulder and stop, making sure you are away from trees or other tall objects that could fall onto your vehicle. DO NOT stop in the middle of a lane under an overpass. This could lead to an accident.
  • Take extra care in a high-profile vehicle such as a truck, van, SUV, or when towing a trailer.
  • These are more prone to being pushed or even flipped by straight-line winds.
  • If possible, orient your vehicle so that it points into the wind.
  • Stay in the car and turn on the hazard lights until the wind subsides.

Caught outside:

  • Take cover in a well-built building or use a building to block the wind if you cannot get inside.
  • If no building is nearby, find the lowest spot and crouch low to the ground.
  • Stay away from trees or power lines, since these are easily felled by straight-line winds.
  • Stay clear of roadways or train tracks, as the winds may blow you into the path of an oncoming vehicle
  • Watch for flying debris. Tree limbs, street signs, and other objects may break and become flying projectiles in the wind.

If you venture outside after the storm has passed, be alert for downed power lines. Do not touch any downed wires or anything in contact with the wires.