Brrr: Tonight will be cold in the North County

Get out the wool blankets: Tonight will be a cold one in the North County.

The National Weather Service has issued a frost advisory for the interior valleys of San Luis Obispo County. The advisory begins at 3 a.m. Friday and continues to 9 a.m.

The NWS says the overnight low will drop below freezing later tonight and areas of frost will form between 3 and 9 a.m.

The overnight low is expected to drop to between 28 to 32 degrees, with subfreezing temperatures lasting for two hours or more.

Friday night will also be another cold one across the North County, so spectators heading to the big high school football game between Paso Robles and Atascadero should dress warmly.

The cause of the chill is the dry air sitting over the Central Coast, thanks to an offshore flow of air. When the evening air is dry, less heat gets trapped and temperatures can drop.