As millions of Americans begin their Thanksgiving travel on Wednesday, severe weather is expected for several of the nation's largest cities, threatening to cause major delays both on the road and in the sky.

Two major storms loom over Americans as they make their annual Thanksgiving pilgrimage, one in the Northeast and one in the Pacific Northwest.

Forecasters say the stormy skies could backup some of America's busiest airports like those in New York City, Washington, D.C., Philadelphia, Boston, Seattle, and San Francisco.

According to a recent AAA survey, 42.5 million Americans will travel 50 miles or more from home this Thanksgiving holiday.

With 90 percent of those traveling on America's highways, the roads will be particularly busy.

The National Weather Service (NWS) reports an active weather pattern for the East Coast, with a front pushing through the Ohio Valley and Mid-Atlantic states into New England.

As this system moves toward New England on Wednesday, it will bring a wintry mix of precipitation, with a mixture of snow and freezing rain possible from upstate New York into upper New England. Total snow accumulations of 4 to 8 inches, the NWS said.

Cities like Burlington, Vt., Concord, N.H., and Portland and Augusta, Me., will be hit particularly hard.

Outside of the extreme Northeast, the main issue facing travelers will be heavy rain and possible flooding.

Wet and slick conditions can cause delays as drivers slow down to take precaution. Thankfully, the heavy rain should subside by midday on the East Coast, though the snow may linger in northern New England.

Out West, damaging winds, heavy mountain snow, and possible mudslides could hamper Thanksgiving travel from Washington to Northern California.

Some areas in Washington have reported winds of up to 70 mph, knocking out power to nearly 10,000 in the Seattle area. Another storm is expected to pound the city on Thanksgiving Day, bringing a new round of rain, wind, and snow.

A strong storm system already hit Oregon. The severe weather prompted a string of warnings from the National Weather Service as wind gusts reached as high as 98 mph at Oregon beaches.

Inland, the stormy weather downed trees and power lines, leaving at least 2,400 Central Oregon residents in the dark. The high winds and rain are expected to taper off later on Wednesday.

For the most part, the busy skies remain open this Thanksgiving holiday.

Philadelphia and Newark airports had delays of between 30 and 45 minutes due to low cloud cover, but the Federal Aviation Administration (FAA) reported few other early disruptions.

San Francisco International Airport was the only West Coast location reporting delays and they were minimal Wednesday morning.

The Transportation Security Administration said it has prepared its workforce for a smooth holiday travel experience for travelers.

Whether you're traveling by air or by land, check out these tips for Thanksgiving travel before you head out.

Tips for the Air

Get to the Airport Early - allow at least two hours for check-in and security lines, even for short domestic flights.

Travel Light - Traveling light will save you time and money, especially with increasingly hefty checked-bag fees.

Print out your Boarding Pass: Get this done at home before you leave and head straight to security when you get to the airport.

Check for Delays - Before you head to the airport, double-check for flight delays. You can also sign up through an airline's website for flight-delay alerts. Also, have a number for your airline handy in case of flight cancellations.

Don't Wrap Gifts - TSA urges travelers not to wrap gifts until they've arrived at their destination. Furthermore, food items such as jams, salsas, sauces, syrups and dips will not be allowed through the checkpoint unless they are in containers three ounces or less and in your one quart zip-top bag.

Don't Forget Your ID - Any passenger 18 and older will need a federal or state-issued photo ID at airport checkpoints. All passengers traveling internationally will need their passport.

Don't Stress - Relax, it's the holidays! Consider splurging on a day pass to an airline lounge for nice seats, tasty drinks, and less crowds.

Check TSA's 3-1-1 for Holiday Travel page for more trips for air travel over Thanksgiving weekend.

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Tips for the Road

Know When to Travel - AAA estimates that 90 percent of holiday travelers will use the nation's roadways, and both Wednesday and Sunday afternoons and evenings will be the busiest times. If you can avoid traveling at these peak times, you'll have a more enjoyable trip.

Know what to Pack - If you're stuck in traffic on the highway in the middle of nowhere, you're going to want to have some drinks and snacks on hand to hold you over. In addition to snacks, make a point of packing for automotive emergencies. Make sure your car has a flashlight, blankets, a car cellphone charger, a can of aerosol tire repair, duct tape, and motor oil ... just in case!

Check Gas Prices - The average price of gasoline is $3.40 per gallon, 51 cents higher than last year. Check AAA's Fuel Gauge Report or the website Gas Buddy to find the best spots to fuel up and save.

Check Road Conditions - If you are traveling in a cold or mountainous region, make sure to check the road conditions before you head out.

Rest Up - Get 6-8 hours of sleep the night before a long trip. Fatigue decreases reaction time and awareness. The last thing you need on your holiday weekend is an accident.

Consider Renting a Car - Daily car rental rates will average $37 over Thanksgiving week, an 11 percent decrease from one year ago. If you're car isn't fit for a long trip, you may want to consider renting one that is.