The notice covered Delaware and Philadelphia counties.

“Temperatures are rising above freezing,” the National Weather Service says.

Frost advisory: here’s what it means

Frost advisories are issued from May to October (but may be extended if necessary) when temperatures, winds and sky cover are favorable for frost development. This is more likely to happen when the temperature is 36 degrees or lower. In some cases, frost is severe enough to end the growing season and is referred to as a “killing frost.”

According to the weather service, if a frost advisory is issued for your area, cover sensitive plants before sunset so that it can help retain heat near the plants, or move the plants indoors for the night , if possible.

Advance Local Weather Alerts is a service provided by United Robots, which uses machine learning to compile the latest data from the National Weather Service.