All areas of Washington State are vulnerable to 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, or 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 Nationa l 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.
- Tornado – A storm with a violently rotating column of air that contacts the ground; tornados usually develop from severe thunderstorms. Tornados 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 4 inches or more in a 12-hour period, or 6 or more inches in a 24-hour period in non-mountainous areas; and 12 inches or more in a 12-hour period or 18 inches or more in a 24- hour period in mountainous areas.
- Blizzard – 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. Blizzards typically are confined to the Columbia River Gorge and Northwest Washington near the Fraser River Valley of British Columbia.
- Dust storm – A storm of dust and debris blown by wind gusts of at least 35 mph, or caused by a downburst from a dry thunderstorm, that reduces visibility to less than one-quarter mile.
- Coastal flooding – Flooding in coastal areas caused by storm surge, astronomical high tides, or a combination of them.
Note: Flooding is a result of severe rainstorms, learn more about floods.
Tips and Information about Severe Storms
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