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What is the monsoon and why is it such a big deal for Arizona?

With an overall hotter and drier setup in place, Arizona will likely experience a late onset of Monsoon 2024.

PHOENIX — Now that we're past June 15, you'll hear the term, "monsoon" used quite a bit. The word monsoon comes from the Arabic word 'mausim,' which means 'season.' The North American Monsoon occurs during the summer across New Mexico, Colorado, Utah, Arizona, and sometimes in Texas, California, and Nevada.  

VERSIÓN EN ESPAÑOL: ¿Qué es el monzón y por qué es un tema importante en Arizona?

The key to the monsoon is the shift in wind direction. Typically, the wind flow across Arizona is westerly; this translates to dry conditions. During the summer months, winds become more southerly. A south or southeast wind helps to transport moisture from the eastern Pacific, Gulf of California, and Gulf of Mexico into Arizona. An increase in moisture helps set the stage for monsoon storms. 

In late June and early July, a ridge of high pressure builds in the Four Corners region. The location and strength of the ridge plays the largest role in monsoon initiation. 

Let's talk about what you need to know. The plural use of 'monsoons' as in, "monsoons are heading my way..." is incorrect. A monsoon is a season, not an individual storm. The singular use of monsoon should be treated as the word, "summer." Both summer and the monsoon are seasons. Referring to "monsoon storms" is correct when describing thunderstorm activity during the monsoon or season. 

During a typical monsoon, Arizona's lower deserts average two inches of rainfall, while the higher mountain ranges receive 16 inches of rain. From mid-June through September, Arizona can receive up to 60 percent of its annual rainfall. The lower deserts can see up to ten days with measurable rainfall, and the mountains can easily experience over 50 rain days. Southeast Arizona and the eastern and central high country receive the highest concentration of storms. The terrain and geographic location of southeast Arizona are more conducive for tapping into that rich monsoon moisture from the south. 

With an overall hotter and drier setup in place, Arizona will likely experience a late onset of Monsoon 2024. Usually, the monsoon doesn't trend busier until July. 

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ARIZONA WEATHER

Drought, wildfires, heat and monsoon storms: Arizona has seen its fair share of severe weather. Learn everything you need to know about the Grand Canyon State's ever-changing forecasts here.

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