Freeze warning for Shiawassee County, 3 a.m. to 8 a.m. Saturday

If you still have tomatoes, peppers or potted plants on the porch, Friday night is the night to bring them in. The National Weather Service in Detroit/Pontiac issued a freeze warning at 1:59 p.m. Friday covering all of Shiawassee County, in effect from 3 a.m. to 8 a.m. Saturday.

The warning says to expect "sub-freezing temperatures as low as 30." The weather service lists the impact plainly: "Frost and freeze conditions could kill crops and other sensitive vegetation." Its instruction to residents is one sentence — "Take steps now to protect tender plants from the cold."

The warning is not just for us. It covers seven counties across mid-Michigan and the Thumb: Bay, Genesee, Lapeer, Midland, Saginaw, Shiawassee and Tuscola.

A freeze warning is issued when temperatures are expected to fall to 32 degrees or below during the growing season, the point at which unprotected plants can be killed outright. That matters here for home gardens still producing in mid-October and for any field crops or nursery stock not yet off the ground.

Practically, the window is short — five hours before sunrise. Covering beds, moving containers into a garage, and disconnecting or draining outdoor hoses and shutting off exterior spigots are the ordinary precautions for a night at 30 degrees.

This is the first freeze warning the desk has logged for the county this fall. Our weather coverage this season has run the other direction: The Current reported on Sept. 3 that a severe thunderstorm watch covered all of Shiawassee County, and on Sept. 4 that 60 mph gusts knocked out power to about 3,300 Consumers Energy customers across at least 10 communities in the county.

What happens next: the warning expires at 8 a.m. Saturday. The weather service did not say in this alert whether a second cold night is expected Saturday into Sunday; updates and any follow-on frost advisories or freeze warnings are posted by NWS Detroit/Pontiac at weather.gov.