A hard freeze warning is in effect overnight into Thursday morning in Tucson and in its metro area, including Green Valley, Marana and Vail, the National Weather Service says.
Through 9 a.m. Thursday, Feb. 3, sub-freezing temperatures are expected.
Across southeastern Arizona, the weather service forecasts the lowest temperatures early Thursday will be 27 in Tucson, Marana, Oracle and Sells; 23 in Green Valley; 17 in Benson; 18 on Mount Lemmon; 23 in Sierra Vista and Nogales; and 16 in Willcox.
"Frost and freeze conditions will kill sensitive vegetation and possibly damage unprotected outdoor plumbing," the weather service warns, adding: "Take steps to protect tender plants from the cold. To prevent freezing and possible bursting of outdoor water pipes they should be wrapped, drained, or allowed to drip slowly. Those that have in-ground sprinkler systems should drain them and cover above-ground pipes to protect them from freezing. Also remember to protect your pets from the cold."
The daytime hours Thursday will remain cooler than average by about 15 degrees, the weather service predicts, but "there will be plenty of sunshine and winds will be light."
The cold temperatures Thursday will slowly warm up to near normal levels by Monday, Feb. 7, then remain there into next week, the forecasters say.
