Some of the first big events of the fair weather season for Northern California are planned in Mid-May for the reliable dry weather but a late-season storm is changing plans quickly.

Light rain has been moving into Northern California Wednesday with a much wetter band set to arrive for the evening commute and well into the night.  The rain might drop up to half an inch in a short period of time and overwhelm drains creating ponding on roads and snarling traffic.

RELATED: Sacramento Local Forecast

Rain will turn to snow in the Sierra with a foot expected over mountain passes by Friday Morning.  This amount of snow is rare for mid-May and many will not be prepared for winter driving conditions, long delays, poor visibility and possible chain controls. Be sure to check CalTrans for conditions before you head out. 

Thursday the addition of thunderstorms will have heavy rain, strong winds, lightning, and hail as extra threats to plan for.

The first break in the weather will be Friday, for the most part, before more rain moves in Saturday afternoon to Sunday.

This pattern of wet weather should easily eclipse the averages for rain and snow in the area and may break daily rain records in some locations.

Plan ahead, assume the wet and cool weather is sticking around into next week. 

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