Dust the cobwebs off the winter jackets, and shut those windows. It’s about to get chilly in the Philadelphia region.

A frost advisory is in effect from 1 a.m. until 8 a.m. Sunday for Philadelphia’s surrounding counties as temperatures are expected to dip into the 30s, according to the National Weather Service’s Mount Holly office. Philadelphia and Delaware Counties are not included in the advisory.

“While the odds of frost will decrease closer to the urban corridor, there is enough potential in the more outlying areas to warrant an advisory ... ‚” the NWS’ posted Saturday in its forecast discussion. “Also, some areas within the advisory may get down to freezing, but not expecting it to be widespread enough to warrant a freeze warning in areas where the growing season remains active.”

Sunday morning will see “some of the coldest low temperatures we’ve seen since mid May,” according to the service, which also recommend gardeners bring plants inside from the cold.

While Philadelphia may not be included in the frost advisory, don’t expect it to be much warmer. The mercury is forecasted to drop to a chilly 41 degrees before daybreak gives way to a mostly sunny Sunday heating up to 63 degrees.

But don’t worry — it’s not quite time to say goodbye to those warmer fall days. Temperatures will range from the the mid-60s to low-70s for the remainder of the week in Philadelphia, according to the NWS' forecast. A mild winter too is expected to be in store for the region.