A shift in the weather pattern has driven below-average temperatures into Southern Arizona, delivering a welcome pause from the widespread triple-digit heat that has gripped the region. The change comes as moisture increases over the area, fueling showers and thunderstorms that are expected to persist through the first half of the week. Forecasters say the added humidity will help keep daytime readings several degrees below what would normally be expected for this time of year.
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Showers and a few thunderstorms are forecast from Tucson westward into the lower desert zones, with more widespread storm activity predicted to the south and east of the city. As storm chances climb, official graphics indicate a marginal to slight flood risk across much of Southern Arizona, shown by green and yellow shading on regional maps, underscoring that some areas will experience heavier downpours as systems pass through.
KGUN9 flood risk graphic showing marginal to slight flood risk (green and yellow shading) across much of southern Arizona as storm chances increase.
The cooler air mass will be most noticeable during the overnight and early morning hours. Tucson is expected to begin Monday near 75 degrees, a notably milder start compared with the recent string of very warm overnights. Higher terrain will see even cooler readings, with many mountain communities dipping into the 60s. A forecast map of morning lows highlights these below-average readings across Southern Arizona, with Tucson near 75°F and higher elevations in the 60s.
Forecast low temperatures for tomorrow morning from KGUN9, showing cooler, below-average readings across southern Arizona — Tucson near 75°F with higher elevations in the 60s.
By Monday afternoon, the cooling trend will keep many communities from topping the triple-digit mark. Tucson is forecast to reach about 96 degrees, while Sierra Vista in Cochise County is expected to see a high near 85 degrees. Overnight lows in Cochise County will be appreciably cooler than in the lower deserts; Sierra Vista is projected to wake up to a low near 67 degrees. Despite the broader cool-down, the western desert pockets will remain the hottest areas, with locations such as Ajo and Organ Pipe forecast to approach 100 degrees during the afternoon hours.
Meteorologists characterize the current setup as a short-lived reprieve tied to increased moisture and storm activity through the middle of the week. The presence of convective showers and thunderstorms will be the dominant feature, particularly across southeast Arizona where coverage and intensity are expected to rise. While many communities will see daytime temperatures fall several degrees below climatological norms, the pattern does not bring a prolonged cooldown — rather, it temporarily offsets the sustained heat that recently pushed many thermometers into the triple digits.
Residents across Southern Arizona should anticipate variable conditions over the next few days as scattered storms move through the region. The spatial distribution of showers is expected to be uneven: localized downpours and thunder could occur anywhere from the lower deserts into the higher terrain, with the greatest concentration of activity south and east of Tucson. The marginal to slight flood risk graphic reflects the potential for heavier rainfall in some storms, which could produce brief periods of intense precipitation where cells train or stall.
Through the middle of the week, the forecast holds the expectation of continued below-average daytime temperatures for much of Southern Arizona, punctuated by periodic rounds of showers and thunderstorms. The weather pattern will afford many communities a temporary break from the widespread heat, while the western desert areas retain the warmest readings. For the immediate 24- to 72-hour window, observers should watch for developments in storm coverage and any shifts in timing that would affect morning lows and afternoon highs across the region.
The National Weather Service has issued a Flash Flood Watch for Monday afternoon through evening across Cochise, Graham, Greenlee, and Santa Cruz counties, where storms east and south of Tucson could bring 1-3 inches of rain on saturated soils, raising the risk of excessive runoff and flash flooding. (@NWSTucson)
The National Weather Service issued the Flood Watch at 11:13 PM MST on Sunday, July 19, 2026; the product names specific areas (including Willcox, Benson, Safford, Douglas, Clifton, Nogales, Sierra Vista and Bisbee) and places the watch in effect from Monday afternoon (noon MST) through midnight Monday night.
NWS also issued Flash Flood Warnings Sunday evening for portions of Cochise County after Doppler radar and automated gauges indicated 1.5–2.0 inches of rain in the Willcox area; the warnings specifically mentioned potential flooding on Route 191, Interstate 10 between roughly mile markers 330–343, and Route 186 between roughly mile markers 327–332 and urged motorists to avoid flooded roadways.