An Extreme Heat Warning will take effect Tuesday morning and remain in place through Wednesday evening for a broad swath of Pima County as temperatures climb into the triple digits and overnight relief remains limited. Forecasters say daytime highs in affected communities could reach as high as 111 degrees, with the warning covering Tucson, Oro Valley, Green Valley, Ajo and Sells. The surge of heat follows a trend of temperatures running 3 to 8 degrees above normal across the region through Thursday before a gradual cooldown is expected later in the week.
Morning temperature map across Southern Arizona showing Tucson at 78°F and Phoenix at 85°F — heat building ahead of an Extreme Heat Warning.
The start of the week will bring another stretch of warm overnight conditions across Southern Arizona, offering little respite from daytime heat, particularly in lower-elevation communities. Many locations are forecast to begin the day with temperatures in the 70s; a few spots are expected to remain in the 80s through the morning hours. Tucson, for example, is projected to see a low near 78 degrees, while Sierra Vista should start Monday near 73 degrees. Ajo may only dip to about 80 degrees overnight, and more elevated communities such as Willcox are forecast to bottom out near 67 degrees.
Dangerous daytime temperatures combined with elevated overnight readings will limit the usual cooling people rely on to recover from daytime heat. Those conditions are expected to persist through midweek within the area of the Extreme Heat Warning, after which forecasters anticipate a gradual easing of the hottest air mass by the latter part of the week. Temperatures across Southern Arizona as a whole are predicted to stay several degrees above typical values through Thursday before the trend reverses toward a more seasonal pattern.
Alongside the heat, atmospheric moisture is forecast to build across Southeast Arizona through the week, setting the stage for the first round of thunderstorm activity in eastern sections as early as Monday. Meteorologists expect initial storm chances to appear over eastern areas Monday and then spread westward through the week as the moist air expands. While the timeline calls for storms to become more likely over additional parts of Southern Arizona as the week progresses, the early activity will favor the eastern zones.
Percent-of-average precipitation map (past 30 days) for Arizona, highlighting pockets of above‑average moisture near Tucson that could boost thunderstorm chances later this week.
Recent precipitation patterns show pockets of above-average moisture near Tucson over the past 30 days, conditions that could help enhance thunderstorm development as the humid air mass expands. The increasing moisture, combined with daytime heating, will be the primary factor in allowing showers and thunderstorms to develop and potentially move farther westward into portions of Southern Arizona later in the week. Exact storm timing, coverage and intensity will depend on how the influx of moisture evolves and interacts with the building heat.
Residents across the warned area should be prepared for sustained hot conditions Tuesday and Wednesday, with limited overnight cooling and the potential for storms later in the week as moisture increases. The forecast underscores the juxtaposition of intense daytime heat and the arrival of humid air that will make nights uncomfortably warm while simultaneously raising the chance for convective activity. Public messaging emphasizes awareness of extreme heat conditions during the daytime peak and monitoring for any hazardous thunderstorm developments as the period of increased moisture unfolds.
Temperatures across much of Southern Arizona are expected to slowly moderate later in the week after the hottest stretch has passed, though forecasters indicate that readings will remain above normal through at least Thursday. Meanwhile, thunderstorm chances will be tracked closely as they shift westward; initial activity is slated for eastern areas Monday with gradual expansion into additional southern and central zones later in the workweek. Local authorities and weather services will continue to update watches and warnings as conditions change.
The National Weather Service in Tucson issued the Extreme Heat Warning at 11:23 a.m. MST on Sunday, July 5, 2026 — upgrading an earlier Extreme Heat Watch — and set the product to be in effect from 10 a.m. MST Tuesday, July 7 through 8 p.m. MST Wednesday, July 8, calling for widespread highs of 107 to 111 degrees across the Tucson metro, western Pima County, the Tohono O'odham Nation and parts of Pinal and the Upper Gila River Valley.
Pima County’s Health Department runs a “Beat the Heat” Heat Relief Network and interactive cooling-center map for residents; in 2025 the county coordinated 33 heat-relief locations (with three additional sites available for emergency use) and distributed thousands of water bottles, cooling towels and other supplies to support vulnerable people during extreme heat events.