Springtime brings a welcome change in seasons. Along with blooming flowers and trees and warmer temperatures, it also marks the start of Severe Weather season. The first week in May is Severe Weather Preparedness Week. Severe weather in warm weather months include thunderstorms and the devastation that may come from them: the potential for flooding, high winds and tornadoes.
A thunderstorm is a rain shower with thunder. Since thunder comes from lightning, all thunderstorms have lightning. A thunderstorm is classified as “severe” when it contains one or more of the following: Hail (3/4 inch or greater, winds gusting in excess of 50 knots (57.5 mph) or a tornado. On average, about 10% of thunderstorms are classified as severe.
Lightning strikes the U.S. about 25 million times each year, kills an average of 47 people annually, and injures hundreds more.[1] When lightning is detected, it is important to take shelter as there is no safe place outdoors when thunderstorms are in the area. “When Thunder Roars, Go Indoors”[2] Once the storm has passed, wait at least 30 minutes after the last thunder is heard before resuming outdoor activities. Once the storm has passed, assess any damage to your property. Contact local authorities if there are power lines down.
High winds can occur during a severe thunderstorm. Winds speeds of 40 to 50 mph can produce localized damage. “Straight-line” winds, which are not associated with any rotation, can exceed 100 mph and can cause widespread damage, and blow objects making them airborne, posing a significant threat to personal safety. If you are outdoors, take shelter in a sturdy building. If not near a building, take shelter in your car. If no shelter is available, stay away from trees and power lines.
A tornado, which is spawned from a severe thunderstorm, is a violently rotating column of air extending from the base of a thunderstorm down to the ground. Tornadoes are capable of completely destroying well-made structures, uprooting trees, and hurling objects through the air like deadly missiles. Tornadoes can occur at any time of day or night and at any time of the year. Although tornadoes are most common in the Central Plains and the southeastern U.S., they have been reported in all 50 states.[3]
If a tornado warning is issued, go to the basement or an interior room in your home/school/business, away from any windows. If you are outside, it is imperative to seek shelter in a sturdy building immediately. Once the authorities have deemed it safe and the tornado(s) has passed, carefully assess your property for damage. Stay out of damaged buildings and contact local authorities if you see power lines down.
Flooding is caused when bodies of water (e.g. rivers, streams, lakes, oceans, etc.) overflow their normal boundaries. Flooding can also occur as storm water runoff accumulates in normally dry areas. Read the Preparedness Bulletin on Flood Preparedness to learn more about how your organization can create an emergency plan to deal with floods, as well as how to mitigate the risk as well as recover from an unexpected flooding event.
For more information about severe weather threats, including mitigation strategies for your organization, read Preparedness Bulletin: Thunderstorms, Lightning & Tornadoes.
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