With storms, snow, delayed flights and industrial action expected in what could be the busiest holiday travel season on record, Americans headed out this week hoping rather than expecting a stress-free trip.

Two major storm systems could bring travel chaos to much of the country, dumping rain and snow on communities and major cities. Since Friday, 17,000 flights have been canceled or delayed across the country due to the severe weather.

Flight tracker FlightAware showed 3,760 delays and 60 cancellations on Monday evening, with San Francisco the hardest-hit transportation hub. These figures include travel to and from the United States. Much more disruption is expected throughout the week.

To make matters even more difficult for some, service workers at North Carolina’s Charlotte Douglas International Airport walked off the job at 5 a.m. Monday after voting to strike on Friday. The Service Employees International Union (SEIU) said it planned to “end poverty wages” and demand “respect at work during the holiday season.”

The striking employees are employees of ABM and Prospect Airport Services, who, among other things, clean aircraft and assist passengers in wheelchairs. Employees there were also on strike in May.

The airport’s online departure board did not immediately show any effect from the strike. Charlotte Douglas is the ninth busiest airport in the United States and handled more than 25 million passengers last year.

Later Monday, several dozen SEIU workers, some holding signs that read, “Airport Workers Will Shut It Down,” rallied at Los Angeles International Airport for better wages and access to affordable health care, potentially contributing to travel delays on the West Coast. The union is calling for an increase in the minimum wage from $25 to $30 per hour.

Millions of travelers are already stressed

It took traveler Marc Supreme 12 hours to get from Peoria, Illinois, to Atlanta on Thursday due to ice and snow, and he says he’s concerned that the week may have more bad weather in store for the Midwest.

“That’s right, especially since I didn’t even know there was weather. I should have checked, so I guess it’s one of those pre-holiday things. Make sure you check the weather because I had no idea I it’s going to take 12 hours to get to Atlanta,” he said as he waited at Hartsfield-Jackson Atlanta International Airport on his way back to Illinois.

Student Emma Welch flew to Atlanta on Sunday from Chicago, where she is studying law, and said she was somewhat concerned about the potential travel disruption with exams looming.

“A little bit, just because of finals and stuff, but hopefully everything will be fine,” she said. She said she didn’t know Sunday would be one of the busiest travel days of the year when she booked her return flight. Instead of showing up three hours early to avoid any complications, she will instead have four hours to spare.

About 80 million people will take to road, rail, air and even cruise ships this week, making journeys of more than 50 miles from home between Tuesday and next Monday.

“This will be the busiest Thanksgiving ever for air travel,” TSA Administrator David Pekoske said on X. “Fortunately, our workforce is also at its highest level ever. We are ready.”

A later Thanksgiving than usual — the last Thursday of this year falls on Nov. 28 — could mean greater travel pressure next Monday and Tuesday as more people travel home instead of extending their visits.

Many are heading south, with both Orlando and Miami’s main airports each expecting 1.9 million travelers during the 12-day travel period.

Weather problems have affected party plans

NBC meteorologist Michelle Grossman said two separate storm systems would bring severe weather to different parts of the country. On Monday and Tuesday, the Rockies and Cascades may experience high winds and snow, making travel in mountain areas difficult. Michigan’s Upper Peninsula could see up to 2 inches of snow, while other areas could see between 1 and 2 inches.

This weather system will then move eastward, causing potential problems on roads with up to an inch of rain from southeast to northeast – although the afternoon could be drier. The storm will intensify and spread on Wednesday, bringing a wintry mix of rain, snow and high winds.

Thanksgiving Day will be a wet day for much of the East Coast, from New England to the South, while northern states could be bitterly cold, up to 80 degrees in Minnesota.

The second storm system will have impacts from California to New England, with widespread heavy rain and snow in the mountain ranges. Between 1 and 3 inches of rain could fall in the Pacific Northwest on Monday, and 10 to 4 feet of snow could fall in the highest parts of the southern Sierra Nevada.

Best times to travel?

The vast majority of trips this Thanksgiving will be on the road, with 71.7 million car trips, surpassing last year’s number by 1.3 million — helped in no small part by lower gasoline prices, which hit a national average this week of $3 per gallon.

Data from transport analyst INRIX shows that Tuesday and Wednesday afternoons will be the busiest times on the roads. But people may not realize that Thanksgiving Day itself is “usually clear.”

“We recommend leaving early in the morning on Tuesdays and Wednesdays, the afternoon hours are the worst,” AAA spokesperson Aixa Diaz told NBC News.

“We always say that traveling during the holidays itself is the best day to travel, not only because if you fly the tickets are cheaper, but there are just fewer people on the roads and in the airports,” she said.

This article was originally published on NBCNews.com