Bear in mind that while Muir Woods' entrance fee is waived on Saturday, you'll still have to pay for your (now mandatory) parking reservation or shuttle reservation. These spots fill up fast, but it looks like there's still availability for Saturday — we'd recommend securing yours now if you're hoping to take advantage of the free National Park Day.

Usually costs: $35 per car

Less than four hours' drive from the Bay Area, Yosemite National Park offers iconic rock formations like El Capitan, incredible waterfalls, ancient giant sequoias and a huge expanse of wilderness. If you haven't been before — and a startling number of Bay Area residents have never visited — Saturday's free National Park Day might be a good opportunity.

But remember, Yosemite is currently experiencing road closures due to snow, so check conditions before you go.

Usually costs: $30 per car

KQED could never condone calling in sick to your place of employment on false pretenses — but we would note that if you start practicing your fake cough now, you'll be all set to take Friday off and drive down to SoCal to enjoy Saturday's free admission at Joshua Tree National Park.

This famously surreal landscape, which is unfortunately still recovering from the damage wrought by some visitors during the recent government shutdown in January, brings together the two distinct desert ecosystems of the Mojave and the Colorado, and offers some of the darkest night skies around.

Certain areas of Joshua Tree are currently closed to climbing and bouldering, so check conditions before you go.

(Bringing kids to a free National Park Day? Saturday, April 20, is also the National Park Service's Junior Ranger Day, offering activities and special programs for kids to earn a Junior Ranger badge. NPS says to just ask a park ranger for details when you get there.)