Autumnal Equinox is Here and Forecasters Are Already Using the 'F' Word—Frost
The National Weather Service has issued a frost warning for Minnesota, just in time for the official start of fall.
Summer officially ended at 9:49 Saturday morning, and already the Twin Cities region is in for a cold snap. Early Saturday morning, officials upgraded a freeze watch to a freeze warning.
The warning is in effect from late Saturday night to Sunday morning. According to the National Weather Service in Chanhassen, temperatures could fall as low as 25 degrees outside the Twin Cities' urban core, which would kill crops and sensitive vegetation
The freeze is a bit early. The first fall frost typically comes around Oct. 5, according to the Farmers' Almanac.
In Burnsville, the NWA predicts that the low will hit 34, two degrees above freezing, with areas of frost from 1 a.m. to 9 a.m. on Sunday morning. However, Mary Schier, editor at Northern Gardener magazine, cautions that the thermometer may be deceptive.
"Frost can form when air temperatures read above 32. Because cold air sinks, the temperature on the ground is often several degrees lower than that above the ground," Schier wrote on Northfield Patch. "So, even if your thermometer reads a toasty 34 or 35, your plants may be shivering below freezing."
A "killing frost" requires temperatures below 28 degrees for several hours, Schier explained, so most plants will make it through this mild cold snap unscathed, though residents should take care to cover their ornamental and vegetable plants.
"Because we have only one really cold night predicted and—take heart!—next week is supposed to be much warmer, it's definitely worth covering the plants that you want to protect overnight on Saturday," Schier said.
She recommended a light bed sheet as cover, which will hold enough warm air to get the plants through the chilly night.