The map shows four states that have been warned of a temperature drop of 30 degrees

Frost warnings are in effect for four states in the eastern United States. Meteorologists warn that temperatures in some of the affected areas could drop by up to 30 degrees overnight.

On Thursday afternoon, multiple National Weather Service offices issued freeze warnings for Virginia, West Virginia, Maryland and Pennsylvania. NWS meteorologists warn that freezing temperatures as low as 30 degrees Fahrenheit overnight Thursday could “kill crops and other sensitive vegetation.”

“Take action now to protect sensitive plants from the cold,” one of the frost warnings said.

More from Newsweek Vault: Online Banks vs. Traditional Banks: Learn the Differences

Daytime temperatures were in the high 50s to lower 70s in most forecast areas where temperatures are expected to be below freezing overnight.

“The high pressure remains under control and will ensure sunny skies. High temperatures this afternoon should range between the upper 50s and lower 70s,” NWS Blacksburg wrote on X (formerly Twitter). “Freeze areas are possible in portions of the mountains through Friday morning, with below freezing temperatures expected in Greenbrier County.”

The freeze warnings were issued by the following NWS offices: Pittsburgh; Blacksburg, Va.; Baltimore; Charleston, West Virginia; and State College, Pennsylvania.

More from Newsweek Vault: 5 Steps to Build an Emergency Fund Today

“A cold night awaits us with freeze warnings and freeze warnings along and west of the Blue Ridge this evening, Friday morning,” the NWS office in Baltimore wrote on X.

“With clear skies, low temperatures will fall into the mid to upper 30s and lower 40s. Sheltered valley locations will be slightly cooler, with mid to upper 20s and low 30s expected,” the bureau said.

More from Newsweek Vault: Checking Account vs. Savings Account: Which is Best for Your Finances?

NWS meteorologist Ben Gruver recounted Newsweek that temperature fluctuations are common at this time of year.

“This is the time of year that we typically see fluctuations where we get quite a bit of warming during the day,” he said. “And then at night, with clear skies and calm winds, we lose all the heating that we had during the day and therefore cool down very easily at night.”

Gruver said this is the first freeze warning for this fall in Greenbrier County, West Virginia.

He added that temperatures are expected to rise over the weekend.

“And then we cool off with another front on Tuesday and Wednesday next week,” he said. “We will probably have another round of frost and freeze by the middle of next week.”

Even more states are under freeze warnings, including West Virginia, Vermont, New York, New Jersey, Ohio, South Carolina, Virginia, Maryland and Pennsylvania.

Frost occurs when temperatures are so cold that dew freezes into ice. Temperatures must be 32 degrees or below, but frost can form even when outside temperatures are above freezing, as temperatures near the ground can be up to 10 degrees colder.