Southwest Climate

Photo courtesy of Daniel Griffin.

From afar, the climate of the Southwest is simple. It's hot in the summer and comfortable in the winter. To the people and ecosystems that populate the region, the seasonal cycles, natural climate variability, and extreme weather create a unique environment.

In the summer, temperatures in the lowland deserts of Arizona and New Mexico regularly top 100 degrees Fahrenheit. During the monsoon season between late June and September, heavy downpours drench the landscape. In the run-up to winter, large tropical storms often blow into the West from the Pacific Ocean. Come spring, a pronounced dry season parches the landscape, priming it for large fires. Seasonal climate changes are also influenced by natural variability. The sloshing back and forth of warm sea surface waters in the tropical Pacific Ocean, for example, creates El Niño and La Niña events that shape winter and summer precipitation. Other climate modes like the Pacific Decadal Oscillation also exert a heavy hand on the climate of Arizona and New Mexico. Seasonal cycles and natural variability leave their mark in the Southwest, and human-forced climate changes threaten to alter these patterns.