“Monsoon” isn't a word most people associate with weather in the United States but there is a monsoon season that arrives each summer in the Southwest, and it has an indirect effect on weather across the rest of the country.
The monsoon season typically gets under way quickly in July, according to the U.S. Climate Prediction Center. It brings a shift from relatively hot, dry weather to relatively cool, rainy weather.
Monsoon season in this country isn't nearly as dramatic as what occurs elsewhere around the globe, especially in India where hundreds have died in torrential flooding.
But the season is crucial for life-giving rains in the desert Southwest. Arizona and New Mexico receive about half their annual rainfall from the rains that accompany their summer monsoon.
Dan DePodwin, meteorologist for AccuWeather Inc., The World-Herald's weather consultant, said this year's season began last week, so relief should be on the way to the drought- and fire-stricken areas.
DePodwin and AccuWeather.com Senior Meteorologist Jim Andrews said a high-pressure system that sets up in the Four Corners area contributes to monsoon rains in the Southwest and to summer storms in Nebraska and Iowa.
That's because Nebraska and Iowa are on the northeast side of the high-pressure system, where storms tend to ride.
By contrast, Texas tends to be dry this time of year because it's on the southeast side of the high-pressure system.
Nebraska and Iowa's moisture is flowing in from the Gulf of Mexico. By contrast, the monsoon rains in New Mexico and Arizona flow mostly from the Gulf of California, DePodwin said.
Sometimes the moisture drawn northward from the Gulf of California into the Southwest U.S. can wrap around the western side of the high-pressure system and eventually flow into the Central Plains, DePodwin said.
As it flows into the Plains, this moisture can aid in thunderstorm development in and around Nebraska and Iowa. Therefore, while most thunderstorms in the Midlands do not directly tap monsoon moisture, a few can be influenced by it, he said.