What it means
Heat trail closures are the gates that swing shut on Phoenix’s hardest summit trails on the hottest days. When the National Weather Service issues an extreme heat warning, the City of Phoenix closes Echo Canyon and Cholla on Camelback, the Piestewa Peak summit trail and its connectors, and four short routes at South Mountain from 8 a.m. to 5 p.m. You can still hike them at dawn. You cannot start up at noon.
Scottsdale visitors run into this constantly, because the Camelback trails are in Phoenix and every concierge sends people to them. The site’s Echo Canyon and Cholla guides cover the trails themselves, and Echo Canyon vs. Cholla covers the choice.
What surprises people is that Scottsdale has no closures at all. The McDowell Sonoran Preserve keeps its sunrise-to-sunset hours through August, and the city’s approach is advice, not gates. “Is it closed?” is a Phoenix question. In Scottsdale the question is whether you started early enough.
Where you’ll meet it
Phone alerts on warning days, signs at the Echo Canyon gate, local news on the first warning of the year, and conversations in which someone insists there is a “105 rule.” There is not, quite.
Where the word came from
The program has a specific origin. On June 16, 2021, during a heat warning, Phoenix firefighters ran three mountain rescues in under 24 hours; twelve were sent home with heat illness and two were hospitalized with acute kidney failure. The United Phoenix Firefighters Association went to the Parks and Recreation Board that July asking it to limit access to the Camelback and Piestewa summit trails when temperatures reached 105 degrees, noting that the city’s rescue helicopter cannot safely fly above 116, which leaves crews to carry patients down on foot.
Phoenix took the idea and changed the trigger. Its 2021 pilot closed Echo Canyon, Cholla and the Piestewa Peak trails on days with a Weather Service heat warning, a forecast product that accounts for overnight lows and early-season heat as well as the high. On August 31, 2023 the board made the program year-round, with closures from 9 a.m. to 5 p.m. In October 2024 it moved the start to 8 a.m., and on March 27, 2025 it extended closures to four South Mountain routes, the Holbert, Mormon and Hau’pal Loop trails and National Trail access from Pima Canyon, while leaving more than 100 miles of that park open.
Dogs got their own rule earlier. Since 2016 Phoenix has barred dogs from its trails when the temperature is 100 degrees or higher.
What it is not
It is not a Scottsdale policy, and it is not a temperature cutoff. The “105 rule” is the firefighters’ original ask, not the law.
The fine print
Phoenix’s own figures make the case for the program. Rescues on the restricted trails fell from 57 in 2021 to 47 in 2022, 30 in 2023 and 35 in 2024, the year the city logged 45 closure days between May and mid-October and 121 days at or above 105 degrees. The program has never been unanimous in spirit: the board’s 2025 decision to restrict a handful of South Mountain routes rather than the whole park, as proposed the previous October, was a compromise with hikers who wanted the mountain left open.
Scottsdale’s policy is the absence of one. The city has not adopted a heat-closure program for the Preserve or Pinnacle Peak, and publishes guidance instead: begin hydrating the night before, drink every 15 minutes, turn around when half your water is gone, and treat any hike that will top 90 degrees as too hot for a dog. That last rule is stricter than Phoenix’s in practice, because rock and decomposed granite run far hotter than the air above them.
The upshot for a visitor is simple. On a warning day, Phoenix decides for you at 8 a.m. Scottsdale leaves the decision to you, and the summer sunrise rules are what the decision should look like.