Thunderstorms are a type of weather distinguished by lightning and thunder produced from a cumulonimbus cloud. They are usually accompanied by large amounts of rainfall and, occasionally, hail.  The storm becomes a severe thunderstorm when winds reach 57.5 miles per hour (92.5 kilometers/hour) or greater, and the storm produces 0.75 inch (0.9 centimeter) or larger hail, funnel clouds or tornadoes. Severe thunderstorms may contain frequent cloud-to-ground lightning and heavy downpours that can cause flooding.

In addition to flooding, thunderstorms can pose other hazards to humans: lightening and tornadoes.

Lightning occurs when a charge is built up within a cumulonimbus cloud and then discharged into the atmosphere. A lightning bolt can be hotter than the surface of the sun, and, contrary to popular belief, may strike in more than one place at once. Some people have been struck by lightning over three times and skyscrapers are like the Empire State Building have been struck numerous times in the same storm.

Tornadoes

A tornado is a violently rotating column of air which is in contact with both a cumulonimbus (storm) cloud base and the surface of the earth. Though they come in any form, tornadoes usually take the shape of a funnel, whose narrow end touches the earth
Tornadoes can be very destructive. Most have winds of 110 mph (175 km/h) or less, are approximately 250 feet (75 meters) across, and travel a few miles before dissipating.  Some tornadoes, however, can have winds of more than 300 mph (480 km/h), be more than a mile (1.6 km) across, and stay on the ground for dozens of miles. Damage from tornadoes is caused not only by high winds but also by flying debris that typically surrounds the lower part of the funnel.

Montgomery County's humid subtropical climate make thunderstorms a way of life for residents, but being used to storms does not mean the county population is not affected by them. Each year dozens thunderstorms affect the area, several of them severe.

Montgomery County was one of the 28 counties declared a federal disaster in early June 2001, when Tropical Storm Allison inundated Southeast Texas, shutdown the Houston Metropolitan area and left 17,000 people homeless.  An overnight soaking of more than 14 inches of rain forced residents from their homes. Bridges, railroads and roads were damaged, and dozens of cars were stranded in high water.

For information about how to prepare for severe thunderstorms and other natural hazards, consult the Montgomery County Emergency Management web site: www.co.montgomery.tx.us/mctxoem