(NEXSTAR) – As the clock ticks closer to the looming weekend deadline, a government shutdown was looking increasingly likely Thursday. A federal shutdown could end up being bad news for hundreds of thousands of federal workers, people who rely on government assistance to pay for food, and those with a trip planned to one of the country’s 425 national park sites.

Since the National Park Service is largely funded through Congressional appropriations, all 63 national parks, plus hundreds of additional monuments and sites, “are at risk of closing Oct. 1” if the government doesn’t reach a deal to keep the government funded, writes the National Parks Conservation Association, a group that advocates for protecting the parks.

As The Hill has previously reported, it’s somewhat unclear what would happen to national parks under an upcoming federal shutdown. The Department of the Interior hasn’t announced its plan, either.

The situation has played out differently in past shutdowns. For example, the parks completely shut down for some time during a 2013 government shutdown. But in 2018, during a partial government shutdown, the parks remained open — just largely unstaffed. That led to problems with trash piling up, illegal offroading, and damage to natural resources. In some instances, Joshua trees at the national park of the same name were cut down as offroaders tried to get around barriers.

In both the 2013 and 2018-19 shutdowns, thousands of National Park Services employees were furloughed, leading to the closure of visitors centers and museums. That’s likely to happen in a potential 2023 shutdown, the NPCA says.

Fewer rangers and park law enforcement on patrol could also make parks less safe for visitors, even if the parks are still accessible. National parks are massive and often have several access points, making them hard to cut off to the public even in situations when they are technically closed.

Some national parks could stay open if states decide to use their funding to keep them up and running. The governors of Arizona and Utah, home to eight national parks combined, have said they’d consider using state funds to keep parks open, The New York Times reports.

Congress has until midnight Saturday night to reach a deal and avert a shutdown.