Monsoons are seasonal wind and rain patterns that form over tropical regions of the world. Throughout the year, warm, moist air from the tropics rises high into the atmosphere, travels toward the poles, then cools and descends into the subtropics. As air leaves the tropics, it draws air from the subtropics into a band near the equator called the intertropical convergence zone (ITCZ).  Subtropical air entering the ITCZ rises, cools, and forms the bands of clouds that produce heavy rainstorms that are the hallmark of monsoons. Seasonal changes in the strength of sunlight and the flow of Earth's Trade Winds shift where the ITCZ sits and monsoons form north and south of the equator. This shifting north and south creates dry winters and wet summers for countries in the region. Monsoons occur in Asia, India, Australia, Africa, South America, and even North America.

The North American Monsoon develops as the summer sun heat warms the continent. During much of the year, the prevailing wind over the monsoon region of northwestern Mexico, Arizona, and New Mexico blows from the west and is dry. In summer, the wind becomes more southerly, bringing moisture from the Pacific Ocean and the Gulf of California. This circulation brings thunderstorms and rainfall to the area, providing much of its yearly precipitation.

The strength and behavior of monsoons varies with geography, ocean conditions such as El Niño cycles, as well as in response to climate events and processes. And those characteristics can have positive and negative results on the state of agriculture, local and national economies, infrastructure, and human health.

Researchers and decision-makers can find a variety of NASA datasets from airborne and space-based platforms to glean new insights into the formation, behavior, and effects of monsoons.