(CNN) — It’s officially autumn, and the US National Park Service has a great way for people to celebrate the equinox this week and a return to cooler weather.

September 24 marks another free entry day to all National Park Service sites that usually charge an entrance fee.

This free day is in celebration of National Public Lands Day.

It was established in 1994 and held annually on the fourth Saturday in September. The NPS says the day “is traditionally the nation’s largest single-day volunteer effort.”

So what’s free?

All entrance fees. That includes not only those marquee national parks such as Great Smoky Mountains, Yellowstone and Yosemite, but all other types of sites the NPS manages:

 National battlefields such as Wilson’s Creek in Missouri
• National historic sites such as the Thomas Edison National Historical Park in New Jersey
• National monuments such as Cabrillo in California
• National seashores such as Canaveral in Florida
• National preserves such as Craters of the Moon National Monument and Preserve in Idaho

Click here for a full listing of every NPS site, which it calls “units.”

Most NPS sites are free all year anyway. Only 108 charge a fee. And as you’d suspect, it’s mostly the big names that ask you to pay to enter: Places such as Arches in Utah, Rocky Mountain in Colorado and Shenandoah in Virginia.

But they’re all free this Saturday.

One catch: “The entrance fee waiver for fee-free days does not cover amenity or user fees for activities such as camping, boat launches, transportation or special tours,” the NPS says.

Planning pays off

If you’re not much of a planner, it might be a good idea to develop the habit — particularly if you want to see a popular NPS site on a free day.

Of those 420+ sites in the National Park System, the top 25 got more than half of the system’s total number of visits last year. Some parks set all-time records for visitors in 2021.

If you have a particular site you wish to visit, check its website first. For instance, some major roads were closed recently in Death Valley National Park (yes, desert regions can get flood damage, too).

Missed out on this free day? There’s one more left in 2022: Friday, November 11 (Veterans Day).

(Copyright (c) 2024 CNN. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

Join our Newsletter for the latest news right to your inbox