Arizona’s Monsoon

Arizona resides within the northern extent of the North American Monsoon. The monsoon season typically begins in early June when active thunderstorms build in central and southern Mexico and then move toward the International Border into Arizona. The monsoon is a season where the dry, westerly winds (winds coming from the west) that typically persist through fall, winter and spring shift to moist, southerly winds (winds coming from the south). The incoming moisture helps build thunderstorm activity across the state.

Terminology: The term “monsoon” refers to a seasonal time of year where thunderstorms are more likely to occur. A monsoon is NOT a thunderstorm, but the monsoon season can help build thunderstorms.

Monsoon thunderstorm activity accounts for roughly half of the annual precipitation in central and northern Arizona, and two-thirds to three-fourths of the annual precipitation in southern Arizona. The short-lived, intense monsoon thunderstorms can often cause flash flooding in areas of steep terrain, low-lying roads, or normally dry washes. Lightning, hail, dust storms, and strong winds are common during the monsoon season.