This holiday season, Congress in the U.S. might find itself playing the role of the Grinch.

If lawmakers cannot reach a consensus by midnight on Saturday, a government shutdown could occur. This situation is raising concerns among Americans about the potential impacts on their everyday lives and the upcoming holiday celebrations.

A government shutdown happens when Congress cannot approve new funding for federal agencies. During such periods, only essential services remain active. These include the military, public safety operations, law enforcement, TSA staff, air traffic controllers, and payments for programs like Social Security and Medicare.

Federal employees who are deemed essential—including millions in the military—will continue working, but without receiving their paychecks. Meanwhile, hundreds of thousands of other federal workers may be furloughed, facing financial uncertainty during what is usually a festive time of year.

Here are a few ways a shutdown might impact everyday Americans.

Will holiday travel be impacted?

Travelers can still take to the skies during a government shutdown. TSA airport screeners and FAA air traffic controllers are expected to report for duty, although they will not receive paychecks until a resolution is reached. During the 2018 holiday shutdown, some air traffic controllers indicated they might leave their positions, contributing to travel delays across multiple airports.

David Pekoske, the TSA administrator, mentioned that around 59,000 of the agency’s 62,000 employees would remain on duty to screen passengers and ensure airport security. However, he warned that “an extended shutdown could lead to longer wait times at airports.” The TSA is anticipating the screening of approximately 40 million travelers this holiday season.

Additionally, passport offices in certain areas might close, creating challenges for travelers needing to renew documents or resolve issues prior to international travel.

Military personnel will go unpaid until Congress acts

Active-duty military members, whether stationed domestically or overseas, will be required to continue their duties during a shutdown without receiving their usual paychecks, as confirmed by Pentagon press secretary Maj. Gen. Pat Ryder. This situation also applies to reservists who are called in for duty and training.

Ryder assured that “the Department of Defense will maintain its primary responsibility and mission to protect our nation and its citizens,” despite the budget stalemate.

Without an approved budget or continuing resolution, military personnel will miss their pay at the end of the month during the holiday season. Reservists who report for duty after December 20 will not be compensated for their service, nor will federal civilian employees who must work during the shutdown. Typically, when Congress resolves shutdowns, they allocate funds to retroactively pay both federal employees and military personnel.

Read more: As Shutdown Looms, $100 Billion in Disaster Relief Hangs in Balance

What will happen to national parks?

Most national parks are likely to close during a federal shutdown, which could disrupt vacation plans for those hoping to enjoy the nation’s scenic wonders during the holidays.

The National Park Service typically has contingency measures in place, which often involve closing most parks and monuments. During the 35-day shutdown that began in December 2018, only a few parks, like the National Mall in Washington, D.C., remained open, but with reduced visitor services, such as limited guides, concessions, and inadequate restroom facilities. The National Park Service estimated a loss of $500 million in visitor spending during a previous 16-day shutdown in 2013.

In Utah, state officials may tap into state funds to keep national parks operational. Governor Spencer Cox expressed frustration over the ongoing congressional negotiations, labeling them as “just embarrassing,” and reassured reporters that the state has plans to ensure the five national parks in Utah remain accessible during a shutdown.

How will safety-net programs be impacted?

Programs such as the Supplemental Nutrition Assistance Program (SNAP), often known as food stamps, and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) will continue operations during a shutdown. However, federal offices managing these programs may offer limited assistance for individuals needing to enroll or resolve issues with their benefits. If the stalemate continues, funding for WIC and SNAP could be at risk.

Furthermore, prolonged shutdowns could disrupt childcare initiatives like Head Start, which provides essential funding for childcare centers to support families facing financial difficulties in accessing preschool education.

Social Security and Medicare benefits will continue without interruption. Nevertheless, federal offices may have limited capacity to assist those trying to enroll or address issues. Benefits from Veterans Affairs, including pensions and disability payments, will also remain available.