What is a Derecho?

A derecho is a powerful, widespread, and long-lived storm characterized by destructive, straight-line winds, often exceeding hurricane-force speeds.

The term "derecho" comes from the Spanish word for "straight ahead," describing the straight-line nature of the wind damage, contrasting with the rotating winds of a tornado. To be classified as a derecho, a storm must produce a wind damage swath extending at least 240 miles (400 km) long, with wind gusts of 58 mph (93 km/h) or greater along most of its path.

Key Characteristics

• Straight-Line Winds:

  Unlike the rotating winds of a tornado, derechos produce winds that move in a straight path, often causing extensive damage over a wide area. 

• Widespread Damage:

  Derechos cause damage over a distance of hundreds of miles, which is much larger than the area affected by a single severe thunderstorm. 

• Long-Lasting:

  A derecho is a long-lived event that can last for hours and produce significant wind damage over a prolonged period. 

• Hurricane-Force Gusts:

  Wind gusts from a derecho can reach or exceed 100 mph, which is equivalent to hurricane-force winds. 

• Destructive Consequences:

  Derechos can result in significant property damage, massive power outages that can last for weeks, and widespread tree damage. 

Classification

• A storm is classified as a derecho after it has occurred and its characteristics are evaluated. 

• The National Weather Service criteria include a wind damage swath of at least 240 miles long and widespread severe reports (wind gusts of 58 mph or greater) along the entire path. 

  
  

Why They Are Dangerous

• Speed:

  Derechos move quickly, leaving residents with little time to prepare for the severe weather. 

• Impact:

  The combination of high speeds and the vast area of wind damage makes derechos a unique and particularly dangerous weather phenomenon.