Winter storms caused thousands of flight delays and hundreds of cancellations around the United States Saturday, with travelers warned to expect a second storm ahead of one of the busiest travel periods of the year.

Read more: Why ‘Hundred-Year’ Weather Events Are Happening More Than Once Every 100 Years

Friday’s storm is wrapping up in the Northeast, where the National Weather Service issued winter warnings throughout New York and Connecticut. Light snow and wind may persist across the region throughout Saturday, with near or below freezing temperatures in areas like Washington D.C., Pittsburgh, and across the Northeast. 

Hundreds of flights canceled

Nearly 800 domestic and international flights in the U.S. had been canceled just before noon on Saturday, with just under 4,000 delays. On Friday, more than 1,700 flights were canceled, with more than 9,000 delays, according to the flight-tracking website FlightAware.

New York’s three major metropolitan airports were among the hardest hit by Friday’s storm. Flights to John F. Kennedy International Airport saw an average of two-hour delays Saturday morning, according to the Federal Aviation Administration, while ground delays are in place at LaGuardia and Newark Liberty International airports moving into midday on Saturday.

Gov. Kathy Hochul of New York declared a state of emergency Friday ahead of the highest snowfall in New York in nearly four years. New Jersey also declared a state of emergency.

In Michigan, ice weighing down on power lines and trees caused more than 30,000 homes and businesses to lose power. Only a few thousand power outages were reported in New York, Pennsylvania, and New Jersey, according to PowerOutage.us.

The highest snowfall in the Northeast reached 11 inches in Hartwick, New York, and just over eight inches in Connecticut. 

Second storm expected to bring more snow

The second storm system is expected to move across the country beginning late Sunday and into Monday, bringing more snow, heavy winds, and rain in different parts of the U.S.

The Transportation Security Administration (TSA) predicts that Sunday will be the heaviest travel day of the year, with an estimated 2.86 million passengers. The busiest day last year was also around the same time, on Dec. 27, when the TSA screened just below 2.85 million travellers. 

The new storm is not expected to be as severe as Friday’s storm. Most of the Midwest and Northeast are expected to receive rain, from Kansas to Ohio and Pennsylvania. The system is forecasted to then move through the East later on Sunday, bringing rain for most and freezing rain to parts of northern New England. Up to 18 inches may fall in the Colorado Rockies as well as in northern New Mexico.

Snow is expected to persist through Monday in the Great Lakes region, in addition to strong winds in Quebec province in Canada. Most of the U.S., however, should expect to see dry weather leading up to New Year’s Eve following Sunday’s storms.

What to do if your flight is delayed

Travelers are entitled to full refunds if they choose not to fly or do not take compensation in the form of credits or vouchers, according to the Department of Transportation (DOT). If your flight is delayed or canceled due to storms, airlines are not responsible for providing additional services, such as hotel accommodations, since weather is considered out of an airline’s control.

The DOT’s dashboard allows travellers to see which airlines have offers following flight cancellations and delays.

Many airlines offer free waivers for those affected by severe weather conditions, allowing for free rebooking or cancellations without fees. Spokespeople from American Airlines, United Airlines, and JetBlue, for example, told Reuters that they have waived change-fees for rebooking on flights that may be affected by the winter weather.