Clear skies over Phoenix this Saturday morning are the calm before a very hot storm. As of Saturday, May 9, temperatures were sitting near 74°F at Sky Harbor, but that mild start will not last. An Extreme Heat Warning from the National Weather Service is set to kick in from 10 a.m. Sunday, May 10, through 8 p.m. Monday, May 11, bringing a stretch of prolonged, dangerous heat to the Valley with highs solidly in the triple digits.
Forecasters are calling for daytime highs in the low-to-upper 100s: about 104°F on Saturday, roughly 105°F on Sunday, and a peak near 108°F on Monday, May 11, which is expected to be the hottest day of the run. Afternoon humidity will crash into the single digits, and overnight lows in the low 70s will not offer much relief. That combination sharply raises the risk of heat-related illness for anyone outdoors or in spaces without adequate cooling. According to the National Weather Service Phoenix, the setup adds up to a major heat risk across the metro.
When Temperatures Peak
The most dangerous stretch each day will be late morning through mid-afternoon, roughly 1–5 p.m., when pavement, sidewalks and other exposed surfaces soak up and radiate extra heat. Winds are expected to stay generally light, with some late-afternoon gusts that can make outdoor labor feel even more draining despite the low humidity. Overnight, do not count on much cooling; evenings will stay warm, limiting the body’s chance to recover before the next day’s heat kicks in.
Where To Cool Off
For anyone who needs a place to escape the heat, Maricopa County operates a Heat Relief Network that includes cooling centers, respite sites and hydration stations. You can call 2-1-1 or check the county’s website for locations and hours, as well as transportation and senior resources for people who need help getting to a cooling site. Visit Maricopa County for details.
Tips For Outdoor Workers And Families
Try to avoid strenuous outdoor activity during the hottest hours. If you have to work or exercise outside, shift the heaviest tasks to early morning or evening, take frequent breaks in the shade or in air conditioning, and drink plenty of water. Wear lightweight, loose-fitting clothing, check on older neighbors, and never leave people or pets in parked cars, even for a short time.
Heat stroke is a medical emergency: call 911 right away if someone becomes confused, faints or stops sweating.
This report will be updated if forecasts or advisories change. Until then, schedule errands and outdoor plans around the peak heat, keep tabs on local forecasts through Monday and, as always, look out for one another this weekend.
