A frost advisory was issued Wednesday evening and overnight lows were expected plunge to near-freezing in Redlands and Loma Linda.
The frost advisory was in effect from 10 p.m. Wednesday to 9 a.m. Thursday in "wind sheltered areas west of the mountains and lower desert areas," the National Weather Service advised.
The overnight low for Redlands and Loma Linda was forecast at 33 degrees Fahrenheit with clear skies.
"A cold dry air mass will remain over the region tonight," the Weather Service advised. "Clear skies and lighter winds will allow temperatures to fall rapidly tonight and again Thursday night. In wind sheltered locations . . . temperatures will likely drop below freezing."
Impacts of freezing temperatures and frost include likely damage to sensitive plants, according to the Weather Service. Sensitive plants could be killed if left uncovered.
There was no word late Wednesday on whether citrus growers intended to smudge or use grove fans to protect vulnerable fruit and trees in Mentone, Redlands and Loma Linda groves.
One of the last times growers smudged in east Redlands and Mentone was during a cold snap in January 2007.