On a typical day during the Arizona monsoon...thunderstorms develop first in the early afternoon over the higher mountains and the Mogollon Rim. Rain cooled air from these thunderstorms, known as outflow, moves down from the high country and into the deserts. Acting like a small scale cold front, this outflow causes the hot and moist desert air to rise, producing thunderstorms. Over the higher deserts, storms generally occur during the mid and late afternoon, while activity is most prevalent over the lower deserts during the late afternoon and evening. On most days, thunderstorm activity ends altogether by around Midnight or 1:00 AM.
As these thunderstorms decay, microbursts, producing severe wind gusts are quite common. Severe thunderstorm wind gusts are defined as those that equal or exceed 57 mph.