A snowstorm is rolling into metro Denver starting Wednesday night, just as Denver International Airport is bracing for a record number of spring break travelers.

Major airlines, including United and Southwest, are preparing for delays and cancellations, allowing passengers to change their flight without cost.

The Denver area is under a 36-hour winter storm warning starting at 9 p.m. Wednesday until 6 a.m. Friday, according to the National Weather Service in Boulder.

Denver is projected to get 8 to 16 inches of snow. Precipitation is expected to be lighter east of the city and forecasts show the airport could get snow accumulation between 7 and 14 inches.

Rain could start before 4 p.m. Wednesday, with thunderstorms later in the afternoon, the weather agency said.

“Travel will be very difficult to impossible” from late Wednesday to Thursday night, the National Weather Service in Boulder said. Those who need to drive for emergencies should have flashlight, food and water in their car.

There are more than 100 delays and 20 cancellations at DIA as of 1 p.m. Wednesday, according to national tracker FlightAware.

The airport just kicked off spring break, one of its busiest travel seasons, and announced Tuesday the period could be record-breaking this year. More than 1.2 million passengers are expected to go through security between March 12 and 30, the airport said, up 6.7% from the same time last year.

The airport is seeing strong demand for flights both in and out of Denver with Coloradans going out of town and last-minute ski tourists coming in for spring break, DIA said.

The airport projected nearly 62,000 passengers going through security on Wednesday and 72,000 Thursday, DIA told The Denver Gazette. The busiest days will be March 16, 17 and 22, which could see more than 80,000 travelers per day.

The airport is preparing for the storm with snow plows ready to clear the runways, airport spokeswoman Ashley Forest said.

Travelers should arrive two hours before their flight and check departure status with their airlines, Forest said. They can also check the airport’s dashboard of wait times for each TSA security checkpoint at flydenver.com/security.

Flyers can also expect to wait in the plane for 10 to 15 minutes for deicing the aircraft before takeoff, Forest said.

Southwest Airlines posted a travel advisory for flights to and from Denver, Colorado Springs and Steamboat Springs. Travelers with flights scheduled between Wednesday and Friday can change their flight within 14 days from the original flight time at no extra cost, according to the airline.

“Our operational planning teams are developing plans with a safety-focus lens to provide the best possible service to our customers in Colorado, while also protecting the integrity of our vast network during this busy spring break travel week,” said Southwest spokesman Chris Perry.

United also allowed passengers to rebook flights scheduled for Wednesday and Thursday. Customers have already taken advantage of the no-fee change and passenger count for Thursday is down 30% than normal, United spokesman Russell Carlton told The Denver Gazette on Wednesday morning.