Additional Hazards

Additional Severe Storm Hazards

Straight-Line Winds

  • Straight-line winds are responsible for most thunderstorm wind damage.
  • Winds can exceed 100 miles per hour!
  • One type of straight-line wind, the downburst, is a small area of rapidly descending air beneath a thunderstorm.
    • A downburst can cause damage equivalent to a strong tornado and can be extremely dangerous to aviation.
    • A “dry microburst” is a downburst that occurs with little or no rain. These destructive winds are most common in the western United States.

Flash Flooding

  • Flash flooding is the #1 cause of deaths associated with thunderstorms and causes more than 140 fatalities each year.
  • Most flash flood fatalities occur at night and most victims are people who become trapped in automobiles.
  • Six inches of fast-moving water can knock you off your feet; a depth of two feet will cause most vehicles to float.


  • Strong rising currents of air within a storm, called updrafts, carry water droplets to a height where freezing occurs.
  • Ice particles grow in size, becoming too heavy to be supported by the updraft, and fall to the ground.
  • Hail causes more than $1 billion in damage to property and crops each year.
  • Large stones fall at speeds faster than 100 mph.