Temperatures are expected to dip below freezing overnight in coastal towns with inland towns reaching the mid-20s, the weather service said.
Skies will be clear with the windy conditions of the day calming down, creating favorable conditions for frost to form on vegetation and crops.
Sensitive flowers, vegetation and crops should be covered or, if possible, brought indoors because the frost could kill them, according to the National Weather Service.
Temperatures are forecast to return to the low 60s over the weekend.
The entire state of Connecticut remains under a Red Flag Warning from 9 a.m. to 8 p.m. Thursday. That means that a combination of strong winds, low relative humidity and dry fuel such as brush, vegetation and wood are creating critical fire weather conditions into Thursday evening.
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