The temperature could reach 80 degrees in the Tri-Cities today for the first time this year, said the National Weather Service.
But with warmer weather and showers predicted, water will be rising in streams and rivers in the Mid-Columbia.
The first storm should arrive in the Tri-Cities tonight. It could produce heavy rain in parts of the region.
A stronger low pressure system could move across the state this weekend. Rain is likely in the Tri-Cities, and the east slopes of the Washington Cascade Mountains could get one to two inches of rain by late Sunday.
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The combination of snow melt and heavy rain could cause streams and rivers to rapidly rise starting Saturday night.
The Yakima River at Kiona is expected to reach the "action stage" of 11 feet by Monday evening. Flood stage is 13 feet.