Early-season triple-digit heat in Phoenix could trigger rare March closures on major hiking trails

What is driving the potential closures

Phoenix is facing an unusually early surge of heat that could push temperatures to or above 100 degrees in March—an outcome that has been rare in the city’s modern weather record. The National Weather Service has previously noted that Phoenix reaching 100 degrees in March has been exceptional, with the late-March 1988 event long cited as the only instance of March triple-digit heat in local records.

If forecast conditions intensify to the point that an Extreme Heat Warning is issued, the City of Phoenix’s Trail Heat Safety Program allows for time-limited closures of select, high-traffic mountain trails. A March closure would be notable because the program is typically associated with late spring and summer, when heat-related rescues rise and the risk to both trail users and first responders increases.

How the city’s Trail Heat Safety Program works

The Trail Heat Safety Program was established in 2021 and has since been updated, including changes approved in 2024 and 2025. Under current rules, when an Extreme Heat Warning is in effect, targeted trails close from 8 a.m. to 5 p.m. The program focuses on a limited set of strenuous, exposed routes that are among the region’s most popular and most commonly associated with heat-related emergencies.

• Camelback Mountain: Echo Canyon and Cholla trails
• Phoenix Mountains Preserve: Piestewa Peak trail system associated with the main trailhead
• South Mountain Park/Preserve: selected trails and segments designated under the program

The city’s heat safety materials emphasize that closures are tied to the issuance of an Extreme Heat Warning, not to a specific temperature threshold, and that restrictions are implemented for defined daytime hours rather than continuously.

Why March matters for public safety and operations

An early-season heat spike can catch residents and visitors off guard because it arrives before many people have acclimatized to summer conditions. It also overlaps with peak outdoor recreation and tourism periods, increasing the likelihood of crowded trailheads on warm days.

Under Phoenix policy, the trigger for heat-related hiking closures is the issuance of an Extreme Heat Warning, with closures generally running 8 a.m. to 5 p.m. on affected trails.

Officials have also expanded heat-response planning beyond trail restrictions. The city’s 2026 heat response plan includes cooling center strategies and seasonal trailhead outreach efforts intended to reduce heat illness and the demand for emergency rescues.

What hikers should watch for

Trail users planning outings during warm periods should monitor official weather alerts and city trail status updates, especially on days when an Extreme Heat Warning is possible. Even if closures are not activated, public health guidance for desert hiking typically stresses starting early, carrying ample water, and avoiding exposed climbs during the hottest part of the day.