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What are monsoons and what do they have to do with summer weather in Utah?
Greg S.
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Awesome question, just in time as we head into late July and August.
The word Monsoon comes from an Arab term "Mausim" or "season" or "wind shift".
During the winter time, winds over Arizona are primarily from the west, but during the late summer the winds shift to the south or southeast bringing in moisture from the Gulf of Mexico and the Pacific Ocean. This shift happens for two reasons, the northward movement of the Bermuda high (over the Atlantic Ocean) and the creation of a thermal low as the land over Arizona gets warmer.
There is still some debate on the exact source of all the moisture. But what we do know is that the thunderstorms formed are from strong surface heating.
A rule of thumb to figure out when the Monsoon season will start is to watch the dewpoint over Phoenix. When it reaches 55 degrees F for 3 or days in a row, conditions for the monsoon have arrived.
Thunderstorms don't form everyday but there are "bursts" and "breaks" in activity. Meaning that we can have widespread storms or we can get cut off and have nothing. There's some links on the right to learn more about this. Monsoon thunderstorms are helpful for late summer rain but lightning is always a danger in very dry places.
Answered by KSL Meteorologist Dina Freedman.
