It’s time to give thanks — for hats, heavy coats and central heating.

Millions of Americans in the Northeast and Middle Atlantic states will wake up to the coldest Thanksgiving in more than a century, with high winds even threatening the iconic Macy’s Thanksgiving Day Parade, meteorologists said Wednesday.

The mercury in Philadelphia is expected to dip to a bone-chilling 29-degree high on Thursday, with similar shivering temperatures also set for New York and Boston at 26 and 21 degrees, respectively, according to NBC meteorologist Kathryn Prociv.

The lowest high temp for a Thanksgiving in New York City history came on Nov. 30, 1871, when the mercury fell to 22 degrees, according to the National Weather Service. The coldest Turkey Day in Boston was 19 degrees in 1873. Philadelphia's coldest Thanksgiving was 28 degrees in 1901.

New York City is also bracing for winds between 15 mph and 25 mph on Thursday, which had Macy’s Thanksgiving Day Parade organizers on high alert Wednesday. The parade will go on, but the 16 giant balloons are another question.

Any sustained winds of 23 mph or gusts of 34 mph would ground the massive inflatable stars of the annual event, organizers said. The decision will be made Thursday morning whether those balloons will be in action.

“At this time, it is too early to make any determinations regarding the flight of those balloons,” Macy’s spokesman Orlando Veras said Wednesday. “In the morning, just prior to the start of the event, the NYPD and Macy’s will make a final determination on the flight of the giant balloons, based on the current weather data available.”

The last time high winds grounded balloons on Thanksgiving Day parade was in 1971. The parade, televised by NBC, starts at 9 a.m. ET.

Boston Mayor Marty Walsh said he’s worried that his citizens will look at the calendar and not realize just how cold it’ll be on Thursday.

“I’m a little concerned about it because I don’t think people realize ... it’s Thanksgiving so everyone knows it’s going to be cold, but no one realizes it’s going to be that cold," Walsh told reporters on Wednesday.

“We kind of think of the weather we’re getting tomorrow more like January weather, than November weather.”

Walsh was particularly worried about people going to high school football games — a Thanksgiving tradition throughout much of New England — without being properly dressed.

“So we’re asking people, if you go to a football game, dress appropriately. Layer,” Walsh said. “Make sure you cover your face, make sure you cover your hands Just be careful when you’re out there.”