Phoenix sits in the Sonoran Desert and receives only around 200 mm (about 8 inches) of rain a year, one of the driest major cities in the country, split between winter Pacific storm remnants and the summer North American Monsoon from July through September. Monsoon thunderstorms are the more dramatic hazard: they can build explosively over the surrounding mountains and desert in the afternoon, bringing dust storms (haboobs), intense lightning, and flash flooding in washes that are bone-dry the rest of the year. Because these storms can go from clear skies to severe within an hour, and because so much of the metro area sits on flood-prone desert wash terrain, radar tracking during monsoon season is a genuinely critical tool. NWS Doppler radar KIWA (Phoenix/Mesa) covers the region.
Learn more: How Does Rain Radar Work? · Open the full Rain Map