Planning a summer trip to Yosemite? This year, you’ll need more than sunscreen and hiking boots to enjoy the country’s most-visited national park.

The iconic California destination is reinstating its reservation system for peak summer dates, so spontaneous road trips might not cut it. Whether you’re driving in, biking through, or just vibing on foot, you’ll need to book ahead, according to KTLA.

“This system ensures all visitors, whether they plan in advance or decide last minute, can experience the park each day,” park officials said in a statement shared by NBC Bay Area. “It also spreads visitation across the day so that visitors have a better experience.”

Reservations are required between 6 a.m. and 2 p.m. during Memorial Day weekend, Labor Day weekend, and daily from June 15 to August 15.

After 2 p.m., it’s first come, first served—but don’t try to jump the line. “If you are planning to visit after peak hours, please do not arrive before 2 p.m.,” officials warned. “Vehicles blocking roads will be cited.”

Reservations are now live on Recreation.gov, and they go fast.

“Reservations sell out almost immediately,” the park warned. “Even if you’re logged on by 8 a.m., there is no guarantee you will be able to get a reservation.”

If you’ve already booked a campsite, hotel stay, or commercial tour, you’re good to go—no separate entry reservation required, per SFGate.

Bottom line: If Yosemite’s on your summer bingo card, don’t wait to lock in your spot.