Severe Weather


A severe storm is an atmospheric disturbance that results in one or more of the following phenomena:

  • Strong winds and large hail
  • Thunderstorms
  • Tornados
  • Rain
  • Snow
  • Other mixed precipitation

Typically, major impacts from a severe storm are to transportation and loss of utilities. Most storms move into Washington from the Pacific Ocean.

The following severe storm elements are considered for this profile (using National Weather Service definitions):

High Winds

Storms with sustained winds of 40 mph or gusts of 58 mph or greater, not caused by thunderstorms, expected to last for an hour or more.

Severe Thunderstorm

Storms that produce winds of 58 mph or greater or three-quarter inch or larger hail.


A storm with a violently rotating column of air that contacts the ground. Tornados usually develop from severe thunderstorms and can produce winds of 100 to 300 mph.

Winter Storm

A storm with significant snowfall, ice, and/or freezing rain. The quantity of precipitation varies by elevation. Heavy snowfall is:

  • Four inches or more in a 12-hour period, or six or more inches in a 24-hour period in non-mountainous areas.
  • 12 inches or more in a 12-hour period or 18 inches or more in a 24- hour period in mountainous areas.


A storm with considerable falling and/or blowing snow combined with sustained winds or frequent gusts of 35 mph or greater that frequently reduces visibility to less than one-quarter mile.

Taking Appropriate Action

It is important to know what actions you need to take to protect yourself, family, pets and property from the impacts of severe weather. Use the resources below to help plan for bad weather.