If you want to camp in Yosemite Valley or at Point Reyes National Seashore, hike the John Muir Trail or venture to other high-demand summer destinations, the reservation clock is now ticking.

At 7 a.m. next Wednesday, reservations for campgrounds in Yosemite Valley first become available for dates when school gets out this summer and the waterfalls are at peak; that would be May 15 through June 14. According to park headquarters, all those reservations could go in a few seconds — perhaps a minute or so at the longest.

It’s a sign of the times for California’s most famous and popular destinations.

The odds of getting drawn for a permit to hike the 211-mile John Muir Trail, which spans from Mount Whitney to Yosemite Valley, can be as low as 60 permits for 11,500 applicants. That’s about the number of people who applied last summer, according to the sources at Inyo National Forest.

The heart of the problem is that California’s population has doubled since 1970, roughly 20 million to just fewer than 40 million, with about the same number of campground spaces at state and national parks and trails in the High Sierra. At the same time, Yosemite, Whitney, the John Muir Trail and, to some extent, Point Reyes National Seashore, Big Sur and many state parks, also now attract large numbers of additional visitors from across the nation and from Europe.

It seems that all these people want to go to the same places, starting with Yosemite, Whitney, the John Muir Trail, Point Reyes National Seashore and other renown destinations. At these marquee sites, the people crush has led to new protocols and pressure to reserve campsites and trailhead permits and launch dates, and also face competition and lotteries for the permits available. The trailhead quotas help the chance of keeping the wilderness experience stellar for each visitor.

Here are the key dates, places and how to work it for your best chances:

Yosemite Valley campsites

Come next Wednesday morning, you should have multiple computers and smartphones linked and signed into www.recreation.gov, get your date, campground in the queue, and the second the clock ticks 7 a.m., click the button to reserve your campsite. Jan. 15 is when dates become available for seven campgrounds in Yosemite for May 15 through June 14, when warmer weather arrives and the waterfalls are at peak. In the next three months, here are the key dates: Feb. 15 for June 15 through July 14; March 15 for July 15 through Aug. 14; April 15 for Aug. 15 through Sept. 14. Reserve at www.recreation.gov or 877-444-6777 (phone calls take too long for high-demand sites). Info: Yosemite National Park, www.nps.gov/yose, 209-372-0200.

State-park campsites

On Friday, dates starting July 10, peak midsummer, will become available for sites at state-park campgrounds. Reservations are now available for six months in advance to the day, 24 hours per day. That means the alarm goes off each night at 12:01 a.m. The campsites that get sold out the fastest are the environmental cabins at Steep Ravine on the Marin coast, beachfront sites at Doheny State Beach at Dana Point (Orange County), and the campgrounds on Monterey Bay. The new “rolling window” means you could book additional consecutive dates not previously available. On Friday, for instance, you could book July 10 and then book additional connected dates after that. Reserve at www.ReserveCalifornia.com. Info: California Department of Parks, www.ca.parks.gov.

Half Dome Lottery

This year’s window is March 1-March 31 to apply for the Half Dome Lottery for dates spanning from Memorial Day weekend to Oct. 15. Rangers said they expect roughly 25,000 to 30,000 applications, which puts the odds of getting drawn at about 20%, better on weekdays, far worse on mid-summer weekends. Apply at www.recreation.gov or 877-444-6777. Info: Yosemite National Park, www.nps.gov/yose, 209-372-0200.

John Muir Trail

The John Muir Trail spans 211 miles from the summit of Mount Whitney to Yosemite Valley at Happy Isles (plus 11 miles between the Whitney Summit and trailhead at Whitney Portal). The JMT has become one of the most desirable trailhead permits in the nation, where the odds of getting drawn are often less than 5%.

From Yosemite: If you exit Yosemite via Donohue Pass south on the JMT to Whitney, apply for your permit through the Yosemite Conservancy, where applications are processed 168 days (roughly 24 weeks) in advance from your starting date. If you have flexibility in starting dates, the new “rolling lottery” application could increase your odds of getting drawn. Permit applications at https://yosemite.org — click on “Experience Yosemite,” and in menu, “Wilderness Permits.”

From Whitney: Permit applications to enter the Whitney/JMT lottery are accepted from Feb. 1 through March 15 at www.recreation.gov. You must enter the lottery and identify specific dates, no more than 21 on the trail, to get a JMT permit. By starting at Whitney Portal and summiting Whitney, the odds of getting drawn (out of 16,000 teams of applicants for the season) can range from 37% on weekdays to as low as 1% or 2% on peak summer Saturdays, according to the Forest Service. Info: Eastern Sierra Visitor Center, Lone Pine, 760-876-6200, www.fs.usda.gov/inyo.

Point Reyes trail camps

From early spring through fall, snagging a campsite at Wildcat Camp on the Coast Trail at Point Reyes National Seashore has become one the hottest tickets in town. Coast, Sky and Glen camps then sell out in short order as well. You can reserve six months ahead to the day. That means that on Friday, you can book for July 10 and through that weekend. A key upcoming target date: March 1 for Sept. 1, where with the new rolling window, you could extend through Labor Day weekend. Reserve at www.recreation.gov. Info: Point Reyes National Seashore, 415-464-5100, www.nps.gov/pore.

Mount Whitney

The 11-mile (one-way) trek to the top of 14,505-foot Whitney, the highest point in the Lower 48, is not only the dream for hikers from around the world, it is the starting point for the southern launch for the John Muir Trail. A lottery is held for each day, May 1 through Nov. 1. Last year, there were 16,842 applications for groups that totaled 84,000 people, 34% of whom won permits, according to staff. Yet for Saturday night, Aug. 2, a total of 11,140 people applied for 60 available overnight spaces. Apply for the Mt. Whitney Lottery from Feb. 1 to March 14 at www.recreation.gov; lottery results posted March 24. Info: Info: Eastern Sierra Visitor Center, Lone Pine, 760-876-6200, www.fs.usda.gov/inyo.

Yosemite Wilderness

Trailhead quotas for access to the wilderness in Yosemite National Park also are filled by a lottery. Yet, unlike Whitney, the JMT and campsites, most people who follow the protocols get their choice of dates and trailheads. Those who wait often do not. Apply for the trailhead lottery 168 days in advance of your hiking start date through the Yosemite Conservancy. To start the process, study each trailhead available and best destinations at www.nps.gov/yose — click on “Play Your Visit,” and scroll down menu, “Places to go” and “Wilderness.” Permit applications at https://yosemite.org — click on “Experience Yosemite,” and in menu, “Wilderness Permits.”

Forest Service campgrounds

The U.S. Forest Service operates roughly 750 campgrounds in 19 national forests in California at mountain lakes, rivers and trailheads. Of these, lakefront sites get booked full on summer weekends. You can reserve sites six months ahead of the date, which means for Friday, you could book for dates starting July 10, with the next five weeks providing opportunities for peak summer, mid-July through August. A key date is March 1, when you could book for Sept. 1 and extend your dates through Labor Day weekend. Reserve at www.recreation.gov.

Tom Stienstra is The San Francisco Chronicle’s outdoors writer. His best-selling book is “Moon California Camping.” Email: tstienstra@sfchronicle.com Twitter: @StienstraTom