A frost advisory issued from midnight through 9 a.m. Thursday has been expanded to most of Suffolk and northern Nassau, the National Weather Service said.
The potentially freezing overnight and early morning temperatures could lead to the formation of frost, forecasters said.
"Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing," the weather service said.
And while both Thursday and Friday are predicted to be sunny with highs in the low 50s by afternoon, both mornings will start with the potential for frost, forecasters said.
Partly to mostly sunny skies are then predicted through next Wednesday, and temperatures will warm up gradually with each day.
Highs in the low 60s are expected by Tuesday, the weather service said.