Most people associate the word monsoon with Asia or India. But few know that the United States has its own monsoon, shaping the climate and economy of the desert Southwest every summer.
Between June and September, a seasonal shift in atmospheric circulation pulls warm, humid air north from the Pacific Ocean and the Gulf of California. When this moisture collides with the extreme desert heat over Arizona, Nevada, and New Mexico, the result is explosive thunderstorms.
The physical mechanism is straightforward:
This is why cities like Phoenix, Las Vegas, and Yuma experience sudden downpours and flash floods despite being in one of the driest regions of North America.
The U.S. monsoon is more than a weather curiosity. Its impacts ripple across society and the economy:
Though little-known outside meteorological circles, the U.S. monsoon plays a central role in the Southwest’s future. As climate change increases the intensity of extremes, understanding and anticipating these storms is vital for water management, agriculture, and urban planning.
The American monsoon is proof that even deserts are not immune to the complexity of climate. What looks like a brief afternoon storm can in reality be a major environmental and economic event.