The National Weather Service in northern Indiana said unseasonably cold air is headed this way.
It said clearing skies Tuesday night and diminishing winds will create conditions for temperatures to rapidly fall well below freezing.
A hard-freeze watch has been issued for all of northeast Indiana and northwest Ohio, in effect from Tuesday evening through Wednesday morning.
It said temperatures will likely fall into the upper 20s and stay there “for many hours.”
Sensitive vegetation could be damaged or killed, including crops, the weather service said.