St. Louis forecasters issue weekend frost advisory for these metro-east counties
National Weather Service St. Louis issued a frost advisory in effect from 1 to 9 a.m. Saturday for several metro-east localities, including St. Clair, Washington and Randolph counties.
Chris Kimble, meteorologist with the NWS St. Louis, said temperatures may drop to the mid-30s Friday night into Saturday morning. While the temperature is likely to stay above freezing, the conditions at ground level could be several degrees cooler, allowing frost to form.
“Any sensitive outdoor plants could be damaged or killed from the frost,” Kimble said. “So anyone who has sensitive outdoor vegetation, they should take actions to protect it. Either bring it inside away from the cold tonight or cover it with a tarp or plastic as that will help keep the heat in and prevent the frost from forming.”
Frost advisories are typically issued when temperatures are expected to reach 36 degrees, Kimble said, and Belleville is right on time for its first frost of the season. Oct. 8 is the average first 36-degree day in Belleville.
The first freeze occurs when the temperature drops to 32 degrees, and Belleville’s first freeze usually comes around Oct. 14, Kimble said.
St. Louis generally sees a later first frost and first freeze date due to the urban heat island, Kimble said. Its average first frost is closer to Oct. 23, and its typical first freeze is Nov. 2.
Although St. Louis normally doesn’t see its first frost until a couple weeks from now, NWS included it in the frost advisory because some areas of the city could see frost, just not as widespread as what’s expected across the river.
The NWS currently forecasts a low of 39 degrees in St. Louis Friday night into Saturday morning.
Who should expect frost?
Here’s where the NWS St. Louis has issued a frost advisory:
Illinois localities
Greene
Macoupin
Montgomery
Bond
Fayette
Clinton
Marion
Washington
Randolph
Calhoun
Jersey
Madison
St. Clair
Monroe
Boone
Missouri localities
Moniteau
Cole
Osage
Callaway
Montgomery
Lincoln
Gasconade
Warren
St. Louis County
St. Louis
St. Charles
Franklin
Jefferson
Crawford
Washington
Saint Francois
Ste. Genevieve
Iron
Madison
Reynolds
