What it means
Your turnaround time is the hour at which you head back, decided before you leave the car and obeyed even if the summit is ten minutes away. It is the single most useful idea in desert hiking, because the desert’s danger is not the climb but the walk out at 10:30 in July, on dark rock, with an empty bottle.
In Scottsdale you hear it two ways. Experienced hikers say it outright: “What’s our turnaround?” Everyone else hears it as the 10 a.m. rule, the summer habit of being off the trail by mid-morning. The rule is a floor, not a target. The site’s summer sunrise rules set the real June schedule: on trail by 5:00, off by 8:00, and in July and August off by 7:30.
The idea also comes in a water version, the rule of halves: turn back when half your water is gone. Whichever trigger hits first wins.
Where you’ll meet it
At the trailhead at 5 a.m. from May through September, in every rescue story on the evening news, on Phoenix’s trail signs at Echo Canyon, and in our comparison of Echo Canyon and Cholla, where summer start times are half the advice.
Where the word came from
Turnaround time is a mountaineering idea. Climbers on big peaks set a hard deadline before leaving high camp, because weather and darkness arrive on schedule and judgment fails near a summit. Valley hikers borrowed the term and swapped the threat: here the deadline is set by the sun and the first 100-degree day, not by afternoon storms or nightfall.
The 10 a.m. rule has no author. It is passed along by trail friends, concierges and firefighters, and no agency publishes a rule by that name. Its logic is simple: by mid-morning in summer, exposed granite has been absorbing sun for hours, shade is gone, and a hiker who started late is climbing just as the temperature passes 100.
Then Phoenix put a clock on it. In July 2021, after the firefighters’ union pushed for action on rescues, the city began a pilot that closed Echo Canyon and Cholla on Camelback and the Piestewa Peak trails from 11 a.m. to 5 p.m. on days with an Excessive Heat Watch, running July 16 to September 30. The program stuck, and in October 2024 the Parks Board expanded it to several South Mountain trails and moved the start to 8 a.m. The city’s official turnaround now arrives two hours before the folk one.
What it is not
A turnaround time is not your expected finish. It is the latest moment you will still turn back, and it should leave the full walk out ahead of the heat. Nor is it about pace. Fast hikers overheat on the same schedule as slow ones; they just get farther from the car first.
The fine print
The closures. Phoenix’s heat trail closures apply when the National Weather Service issues an Extreme Heat Warning, the alert explained in excessive heat warning. The restricted list covers Echo Canyon and Cholla on Camelback, the Piestewa Peak Summit trail and its neighbors, and the Holbert, Mormon, Hau’pal Loop and National trail access at South Mountain, from 8 a.m. to 5 p.m. Phoenix also bars dogs from city trails at 100°F and above.
The results. The city reported in 2025 that from 2021 to 2024 rescues fell 37 percent on Camelback and 43 percent on Piestewa Peak, though Phoenix Fire still answered 68 mountain rescues across four trail systems between May and September 2024. Closures shift the problem; they do not end it.
Scottsdale’s approach. The McDowell Sonoran Preserve has no heat closures. Its trailheads open at sunrise and close at sunset all summer, and the Conservancy’s advice is blunt: estimate the water you want and double it, and if your face goes bright red or you stop sweating, find shade and sip. The judgment, and the turnaround, are yours.
A useful default. Start at first light, set a clock time and a half-water mark, and treat dry heat as no less dangerous than the humid kind.