06/10/2026
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Confidence is increasing that remnant tropical moisture associated with former Tropical Storm Boris over southern Mexico will begin spreading northward into the Desert Southwest late this week, continuing into the weekend. The subtropical ridge will nudge east, paired with a weak upper low developing off the Baja Peninsula. This setup allows southerly flow to transport the moisture into southern Arizona and portions of far southeastern California from Thursday through the weekend. Atmospheric moisture values rise to 1.0 to 1.5 inches across southern Arizona by the weekend. This quality moisture surge is more than enough to support shower and thunderstorm development, favoring the higher terrain. The first very isolated storms may develop as early as Thursday near the International Border and mountains of southern Arizona. Rain and storm chances are expected to increase Friday through the weekend as deeper moisture overspreads the region. The highest coverage of showers and storms is expected across southeastern Arizona, the Sky Islands, White Mountains and areas near the New Mexico border where terrain-driven convection will be favored each afternoon and evening with the addition of daytime heating - some of those storms may drift into the valleys at times. Across southeastern California, including portions of Imperial County and areas near the lower Colorado River Valley, moisture levels will increase as well. While storm coverage is expected to be less than in Arizona, isolated showers and storms may develop near the higher terrain and drift into adjacent desert locations. Be weather aware if you have weekend boating, camping or hiking plans - storms could produce lightning, gusty winds and localized flooding