Now, it seems, they're going to be able to open as usual.
Trump's federal hiring freeze had left park officials across the country wondering if they would still be able to start hiring in February and March for the summer season.
Now it appears they still can hire those seasonal employees.
"As long as the Department of Interior (which oversees the park service) gives advance notice to its OMB resource management office, the hiring of seasonal workers should be allowable," Coalter Baker, a US Office of Management and Budget spokesman, told CNN.
Seasonal employees are critical to the park service during the high season, NPS spokesman Tom Crosson told CNN.
"They help parks throughout the system provide quality and safe experiences for our visitors during peak visitation periods," Crosson said.
"The National Park Service will continue to work with the Department of the Interior, Office of Personnel Management and Office of Management and Budget Administration to ensure that we meet the needs of park visitors across the system throughout the year."
The exemption has parks advocates breathing a short-term sigh of relief.
"There was great anxiety building with the uncertainty surrounding seasonal hires," said Maureen Finnerty, chair of the Coalition to Protect America's National Parks
, a group of retired NPS professionals.
"Hiring seasonals is good news for visitors, park resources, and communities surrounding parks," Finnerty said. "It will create jobs and have a positive economic impact on these gateway communities."
Laura Cooper had already booked a trip for family and friends to Glacier National Park in July, and the Seattle resident says she's feeling relieved.
"Part of the reason we moved to the Pacific Northwest was to have our children grow up around the national parks," said Cooper, who has three children. "Maintaining and staffing these parks is vital for the next generation, especially with so many electronic distractions today. For our family, we see it as an important part of our children's education."
The best known national parks
The park service agency oversees 417 sites on 84 million acres around the country, including the headliner national parks, battlefields, civil rights sites, lakeshores and seashores, and even the White House.
The best known sites may be the 59 national parks.
Great Smoky Mountains National Park had 10.7 million visits in 2015, making it the most popular of the 59 headliner national parks. Grand Canyon National Park came in second place (5.5 million), followed by Rocky Mountain National Park (4.16 million), Yosemite National Park (4.10 million) and Yellowstone National Park (4.1 million) rounding out the top five parks.
Many of the 417 park sites depend on 8,000 seasonal employees, many of whom are teachers, college students and people trying to become permanent employees, to supplement the work of about 12,000 permanent and temporary employees and some 400,000 volunteers, according to 2015 data. (The park service hires another 2,000 seasonal workers during other parts of the year.)
Many seasonals come back year after year, creating a community in the parks where they work.
Jennifer Ladino, who worked at Grand Teton National Park for 13 summers from 1996 to 2008, did many different jobs during her time at the park.
Ladino, now an English professor at the University of Idaho, worked at the entrance desk, the public affairs office, handed out backcountry permits and shared safety information during her summers at Grand Teton.
"Seasonals staff the entrance stations and the visitor centers, perform difficult labor related to infrastructure and trail maintenance, manage fires, conduct search and rescue operations, and much more," said Ladino, whose next book will be about about national memorials in the US West.
Making a bad situation worse
And while it's good news for the summer season, advocates say the hiring freeze means the parks can't hire permanent employees.
"Parks are already understaffed, and many employees that remain are edging closer to retirement," said Theresa Pierno, president and CEO of the National Parks Conservation Association. "Park rangers are already forced to do more with less, and while the agency will now be able to hire seasonal workers for the parks' busy summer season, a hiring freeze only makes a bad situation worse.
"If there isn't a total exemption for the park service from the hiring freeze so parks can hire permanent staff or worse, if they are forced to further reduce their ranks, it would add insult to injury and further hurt an already understaffed agency," Pierno said.
"Parks need more people, not less, to handle record-breaking crowds heading into our parks, care for our natural resources and tackle parks' $12 billion infrastructure repair backlog."
Pierno was referring the park service's list of $12 billion in deferred maintenance
across the park system. About half of that backlog is for road work. The rest is for work on wastewater plants, buildings, campgrounds, trails and other projects.
"The backlog is likely to continue to grow over time under current budget scenarios although Congress, during the Centennial (in 2016), provided a modest increase for deferred maintenance and the ability to raise additional funds through partnerships," NPS spokesman Jeffrey Olson told CNN.
"For that we are grateful. Our current strategy remains prioritizing maintenance needs to address visitor and employee safety and high priority facilities."