The icy touch of frost was widespread across San Luis Obispo County early Friday as a winter cold snap plunged the region into lows from the 20s to 30s.

The low temperature recorded at the Paso Robles airport was 27 degrees, while Cal Poly had a reading of 33, the National Weather Service said. Neither mark set a record.

The chill led officials with the Prado Day Center in San Luis Obispo to open their building as an overnight warming station for homeless people. It will reopen for that purpose at 4:30 p.m. Saturday and again at 4:30 p.m. Sunday. Volunteers are needed to help staff the shelter in the overnight hours.

The low in San Luis Obispo tonight and Sunday night could be in the upper 20s.

Paso Robles could see temperatures near 20 degrees tonight and Sunday.

The weather service issued a freeze watch for tonight into Sunday morning. Such a watch is called when the temperature is expected to drop below 28 degrees for at least two consecutive hours. Homeowners are advised to protect any plants that might get burned by below-freezing temperatures.

Forecasters say over-night lows will remain chilly well into next week. Nightly temperatures in San Luis Obispo won’t get above freezing until Tuesday.

It will be Thursday before Paso Robles emerges from below-freezing lows.