Cloudiest U.S. County: Clallam County, Washington

Clallam County, Washington (Olympic Peninsula, including Forks and Port Angeles) holds the distinction of the cloudiest county in the contiguous United States, averaging approximately 225 overcast days per year.

The combination of:

• Marine west coast climate (constant Pacific moisture)
• Orographic lift from the Olympic Mountains
• Prevailing westerly storm tracks

creates persistent low cloud, drizzle, and fog. Nearby Grays Harbor and Pacific Counties (WA) and parts of Southeast Alaska (not county-based) rival or exceed this cloudiness.