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(CNN) - Millions of Thanksgiving travelers in the United States will be hit this week by several storms, including a dangerous system that threatens parts of the West Coast.
From California to Michigan, more than 20 million people are under winter weather warnings, alerts or warnings, CNN meteorologist Dave Hennen said. And we are still 26 days before the official start of winter.
A "historic" storm is heading towards southwest Oregon and northwest California on Tuesday and Wednesday, the National Weather Service (NWS) said. The storm is currently forecast to rival the strength of a category 1 hurricane and accumulate wind gusts of up to 119 km / h, stronger than the hurricane's strength, said CNN meteorologist Judson Jones.
The pressure could fall to a record low for November and a historic record for the region, the NWS said.
This is what you can expect from coast to coast:
California: get ready for flash floods and snow
A severe storm will hit California this week, bringing heavy snowfall in the mountains and heavy rains to the coast and valleys, Hennen said.
"Winter storm warnings cover the Sierra, where snow will be measured in feet from Tuesday through Friday," he said.
Up to 2 feet (60 cms) of snow could cover the mountains outside of Los Angeles.
In other parts of Southern California, more than 10 million people are under surveillance of flash floods from San Diego to Anaheim, where 3 to 7.6 centimeters of rain could make this Thanksgiving Day soaked.
Winter️ A Winter Storm Watch has been issued for late Tue thru Fri eve for the mountains
⚠️ A Flash Flood Watch has been issued for late Tue thru Thu eve for all areas west of the mountains
Check out the updated rainfall and snowfall estimates for the storm below 👇 #cawx pic.twitter.com/smuYrhQ1uq
- NWS San Diego (@NWSSanDiego) November 24, 2019
The Rocky Mountains and the Midwest: take out your shovels
Climate warnings are in effect for Denver, where a winter storm will likely throw 25 to 38.1 centimeters of snow in the next few days, Hennen said Monday.
Some parts of the Rocky Mountains can see 2 to 3 feet (60 cms to 1 meter) of snow.
"The same storm will spread across the Midwest and probably shed 20-30.5 centimeters of snow in Minneapolis," he said. Iowa and Michigan will also be hit with snow starting Wednesday.
"Winds and rain will slow down airports from the Midwest all day (and) to the main northeast centers during the afternoon and evening," Hennen said.
Before the winter storm, Delta said it is issuing exceptions that will allow passengers traveling from, to or through Denver on Tuesday and Minneapolis on Wednesday to change their travel itinerary without incurring a change fee.
Further south, in the plains and the Mississippi Valley, stormy winds and strong storms will develop from Tuesday to Wednesday.
The Northeast: Airplanes and Charlie Brown may not take off
Fierce winds and rain could wreak havoc on Wednesday for airline passengers in the northeast.
You know it's bad when Macy's Thanksgiving Parade has to land those huge and iconic balloons.
READ : Macy's Thanksgiving Parade may not have giant balloons this year
Balloons cannot be flown when sustained winds exceed 37 km / h and gusts exceed 54 km / h, according to New York City regulations.
There is a good reason for that. In 1997, the Jack in the Hat balloon wounded four people after strong winds forced him to get lost.
Once the northeast recovers from the brutal winds on Wednesday and Thursday, travelers returning home on Sunday will face another round of tumultuous winds and rains.
Everywhere: take your patience to the road
If you drive to see your loved ones this Thanksgiving, expect more company along the way.
AAA predicts the second largest number of travelers in more than a decade this Thanksgiving week.
Car associations expect 1.6 million more travelers on the road compared to last year, thanks in large part to lower gas prices.
Wednesday is expected to be the most congested day of the week, and cities like Atlanta, Los Angeles, New York, Boston, Houston and San Francisco could see more than three times their normal traffic levels.
Judson Jones, Taylor Ward, Allison Chinchar, Haley Brink, Amir Vera and Darran Simon contributed to this CNN report.