For trick-or-treaters in many parts of the country, this Halloween may not have that familiar chill in the air.

More than 30 cities across the Northeast could set record-high temperatures on Thursday, including Boston, New York and Washington, D.C. Many Midwestern cities, too, are expected to see temperatures 10 to 30 degrees warmer than usual for this time of year.

Boston is expected to reach a high of 80 degrees Fahrenheit, which would make it one of the warmest Halloweens in the last 80 years, according to Caitlyn Mensch, a forecaster with the National Weather Service in Boston. The city’s current record of 81 degrees was set on Oct. 31, 1946.

“It’s quite above normal for this time of year,” Mensch said.

Given the unseasonable warmth, she recommended that trick-or-treaters make an effort to stay hydrated and wear sunscreen if it is still light out.

New York City on Thursday is forecasted to hit 78 degrees, and a high of 81 is expected in Washington, D.C.

In the Midwest, temperatures will be similarly balmy for late October. Cleveland could reach 78 degrees, and the forecasted high of 68 degrees in St. Louis could rank this year within the top 30 warmest Halloweens in the area over the past century, said Jared Maples, a meteorologist at the National Weather Service’s local office in St. Louis.

Chicago may see temperatures climb to 68 degrees. That would make this Halloween one of the 10 warmest ever recorded there, according to Zachary Yack, a meteorologist at the Chicago branch of the National Weather Service. Normal Halloween weather for the area is 56 degrees, he added.

“We’ve had a fairly warm pattern stretch across much of the Great Lakes and Midwest here in the last several weeks,” Yack said. “We’ve been tracking this high pressure, and high pressure tends to lend to sunnier skies and, in most cases, warmer conditions.”

Forecasters expect temperatures to cool by the weekend.

Autumn overall has been warmer than usual in several parts of the country. Much of the western United States sweltered through an unusual heat wave in early October, with temperatures that climbed well into the triple digits in cities like Phoenix, Las Vegas and Napa and San Jose, California. Dozens of new daily heat records were set across California, Arizona and Nevada.