Summer conditions arrived in Tucson on Monday as the thermometer climbed to 99 degrees, the first day of meteorological summer and the first above-normal high since May 16. Forecasts indicate that highs will remain near to slightly above normal through much of the week, with only a modest cooling trend expected late in the week and into the weekend. That brief moderation follows the arrival of moisture from the east that set up a midweek window for the season’s initial thunderstorm activity across parts of southeast Arizona.
National Weather Service forecast graphic for southeast Arizona showing temperatures, probability of precipitation and dew points — NWS Tucson highlights the next chance of showers late Wednesday into early Friday.
Meteorological guidance points to a sequence that begins with moisture advancing into New Mexico on Tuesday, which is expected to trigger scattered storms there and allow low-level humidity to spread westward into eastern portions of southeast Arizona by Tuesday night. That increase in moisture is the principal factor that will create afternoon thunderstorm opportunities on Wednesday and Thursday. The greatest likelihood for convective activity is focused over mountain ranges in Greenlee, Graham and Cochise counties, where terrain and the incoming moisture combine to favor storm development.
Photographs from the region illustrate the type of weather pattern anticipated: thunderhead buildups over local neighborhoods and distant ranges are a visual sign of the increasing midweek storm chance. While the highest probabilities are concentrated in the higher elevations, eastern Pima County, southeastern Pinal County and Santa Cruz County lie along the western fringe of the moist plume and could see isolated activity as the system advances. Forecast probabilities for storm occurrence vary markedly by location, with Wednesday currently expected to be the most active day and probabilities ranging roughly from 10 percent up to about 60 percent depending on position and elevation.
Thunderstorm clouds building over a Tucson-area neighborhood with mountains in the distance, illustrating increased midweek storm chances described in the report.
Forecasters caution that the storms expected along the western edge of the moisture plume are not projected to deliver heavy rainfall. Some thunderstorms could be predominantly dry, producing lightning with little precipitation reaching the ground. That pattern raises the familiar fire-weather concern where lightning strikes occur over terrain that has remained dry through the late spring and early summer months. The forecast signals a rapid shift in conditions late in the week: the moisture should clear quickly by Friday, though isolated storm chances may linger a bit longer across the White Mountains before a dry, westerly flow becomes dominant heading into the weekend.
Looking beyond the immediate seven-day window, the medium-range outlook for June 8 through June 14 tilts toward above-normal temperatures, with probabilities in the low- to mid-50 percent range. Forecasters have highlighted June 11 through June 14 as the period most likely to bring the first truly hot temperatures of the season. That signal in the 8-to-14-day outlook indicates a trend toward warmer conditions for that stretch of early to mid-June, following the episode of early-week moisture and the brief cooling that may occur as the moisture departs.
Through the week, residents and visitors can expect a pattern that begins with a pronounced daytime heat signature and then briefly shifts into a moisture-enhanced regime midweek, mainly affecting higher terrain and eastern portions of the region. By late week and into the weekend, drier air and westerly flow should reduce thunderstorm chances and allow temperatures to settle back near to slightly above seasonal normals before the possibility of a more extended heat period later in the month. Forecasts will continue to refine thunderstorm probabilities and timing as the moisture surge and its interaction with local terrain evolve.