It's a Thanksgiving tradition. But it's not immune to weather.

Due to high winds expected in New York City Thursday, some of the balloons set to fly in the Macy's Thanksgiving Day Parade may be grounded for the holiday, according to the New York Times.

The Times reports city regulations ban larger balloons from flying during sustained winds stronger than 23 miles per hour or wind gusts stronger than 34 miles per hour. As of Tuesday afternoon, meteorologists predicted sustained winds of up to 25 miles per hour, with wind gusts up to 40 miles per hour, above the limit to ban the giant balloons from flying.

The biggest balloons are 50 to 60 feet long, sometimes equally high, and they require dozens of people to handle them. 

If the balloons are grounded Thursday, it would be the second time in history it's happened. The first time was in 1971. However, the Times reports, if the larger balloons are grounded, Macy's has a supply of 40 smaller balloons to take their place.