Key keywords: Arizona weekend weather forecast, Phoenix summer high temperature, Southwest monsoon humidity, Arizona rain probability increase, Sonoran Desert thunderstorm risk, Maricopa County heat advisory, Arizona flash flood warning The National Weather Service (NWS) Phoenix office has released its latest 3-day weather outlook for Arizona, warning residents of a sweltering, humid weekend paired with growing chances of afternoon and evening thunderstorms across most of the state starting Friday. For central Arizona, including the greater Phoenix metro area, daytime high temperatures will hover between 107°F and 113°F throughout the weekend, a slight dip from last week’s record-breaking 118°F peak, but far more uncomfortable due to spiking humidity levels driven by the annual North American monsoon. Relative humidity values will rise to 35% to 50% during overnight hours, and stay between 20% and 30% during the hottest parts of the day, pushing heat index values as high as 118°F by Saturday afternoon. The NWS has issued a heat advisory for all of Maricopa, Pinal, and Yavapai counties, effective from 10 a.m. to 8 p.m. both Saturday and Sunday, urging residents to avoid strenuous outdoor activity during peak heat hours, stay hydrated, and check on elderly neighbors, unhoused populations, and pets that may be exposed to high temperatures. Rain chances will climb steadily over the three-day period: just 15% of isolated showers are expected Friday afternoon, mostly in mountainous areas east of Phoenix, before rising to 35% on Saturday and 45% on Sunday for the entire central and southern regions. Meteorologists note that storms will be fast-moving but capable of producing intense, short bursts of rainfall, wind gusts up to 50 mph, small hail, and dangerous lightning. The Arizona Department of Emergency and Military Affairs has also issued a flash flood watch for all low-lying areas, dried creek beds, and desert hiking trails, reminding drivers never to cross flooded roadways, as even 6 inches of moving water can sweep away a standard sedan. For northern Arizona, including Flagstaff and the Grand Canyon National Park, temperatures will be milder, ranging between 82°F and 90°F, but rain chances are even higher, hitting 60% on Sunday, with park officials warning hikers to avoid exposed ridge lines during storms and reschedule backcountry trips if possible. Local businesses across the state are adjusting their plans for the weekend, with outdoor event organizers moving concerts and farmers markets to earlier morning slots, and convenience stores stocking extra water, ice, and cooling supplies to meet expected demand.