(CNN) — Fourth of July weekend is approaching, and most of the United States will see rain chances through Monday. As airports fill up with the most travelers in years, widespread showers and thunderstorms are likely to impact air travel in some areas, causing delays and cancellations.

The southern U.S. will see the most exceptional rain, with the heaviest chances Saturday. The Northeast will see thunderstorms during peak weekend travel on Friday and Saturday afternoon. And besides monsoon thunderstorms, dry conditions creating severe drought in the Southwest will pose a threat for wildfires.

Here is what to expect and when.

The highest probability for rain will be in the East

Cloud coverage and storms will bring cooler temperatures for many, which is a big relief for those still recovering from June’s massive heat wave.

But this cooler air brings the chance of rain and occasional thunderstorms, which could impact travel to parts of western New York and Pennsylvania in the earlier part of the weekend.

“As the colder air advances through, thunderstorms will develop, creating a risk for lightning, gusty winds and even a few flight delays,” said CNN Meteorologist Chad Myers.

Parts of Michigan, Ohio, Pennsylvania and New York have marginal risk (level 1 of 5) for thunderstorms, wind and hail on Friday.

On Saturday, the weather system pushes further east, creating a slight risk (level 2 of 5) for thunderstorms for eastern New York, Philadelphia, Boston, Washington, D.C. and parts of New Jersey.

Flight delays at busy airports like New York, Chicago and Detroit are all possible starting Friday. Airports across the U.S. are already reporting high customer volumes that they haven’t seen since before the pandemic and are already trimming some of their flights.

The weather will likely add to the misery of the already expected delays.

Luckily, these storms are expected in the afternoon, so early flights will have a chance of running on time. Later in the day, storms are more likely to create delays and travel headaches.

By Sunday the rain clears out of the Northeast and cool, dry air builds in, according to Myers.

The same may not be said for the Southeast, where rain chances stretch into Monday.

Fourth of July weekend will be a soaker for the South

The southern U.S. will see the most moisture through the weekend, including popular Independence Day destinations like Atlanta, Houston and New Orleans.

Atlanta, the busiest airport in the world, could see “Mother Nature’s fireworks,” as thunderstorms and rain are likely from Saturday through Monday. Delays and cancellations are expected as storms move through Georgia.

The Weather Service office in Atlanta says the main threats in the coming days are strong storms, heavy rainfall, gusty winds and frequent lightning. Up to two inches of rain is expected over the weekend, and there’s a possibility firework shows could be rained out.

Delta, based in Atlanta, announced a travel waiver from July 1 to 4 for customers to reschedule their flights to after the holiday.

“We are providing more flexibility to customers for making changes to their flight schedule ahead of the busy July 4th holiday weekend as we expect to carry customer volumes over the weekend not seen since before the pandemic,” the Delta website said.

New Orleans and Houston residents should prepare for a wet start to the weekend.

A tropical disturbance will bring heavy rain chances through Saturday, where rain totals can reach up to six inches, according to the Weather Service in Houston.

The heat returns on Sunday, making for a clear and warm end to the holiday weekend. Something the rest of the state and Southwest are all too familiar with.

The West is expected to stay dry in areas with long lasting drought

The western U.S. is staying mostly clear for the holiday weekend, creating the lowest chances for travel delays and cancellations. But parts of the Southwest are in desperate need of rain.

Severe drought across the southwestern U.S. has created dry and fire-prone conditions. Some areas have burn bans in place to prevent wildfires caused by firework use.

“Across most of the western states, the drought is so severe that some firework displays are actually canceled again this year,” Myers said. “The ground and vegetation are so dry that one spark could cause a wildfire.”

Flagstaff, in northern Arizona, will have a laser show to avoid fire risk. The area has already seen severe wildfires this year.

Occasional monsoonal thunderstorms will pop up over the weekend over the Arizona-New Mexico border, creating a slight flash flood risk for wildfire burn scars.

California will have the best firework views this weekend with very clear conditions Friday through Monday. But drought prevails in southern California, and the National Weather Service in Los Angeles warns residents to use caution with fireworks.

Colorado and eastern Utah are expected to receive the heaviest rainfall through Monday. Thunderstorm chances heat up in the afternoon hours of Friday into Sunday, which may slow travel in Denver. Monday looks to be the clearest day in Colorado.

Cool temperatures will take over Saturday through Monday in the Northwest. Oregon and Washington might see some scattered showers but will have a mostly dry holiday.

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