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North American Monsoon

What is the North American Monsoon?

The North American Monsoon (NAM) is a shift in the weather pattern that allows for continuous moisture to stream northward from the Gulf of California and into the southwestern region of the United States.

The term "monsoon" is derived from the Arabic word "mausim", which means season.

When does the NAM occur?

The North American Monsoon can begin as early as June 15th and extend through September 30th.

The pattern typically happens when a high pressure (clockwise rotation) settles over Texas and a low pressure (counterclockwise rotation) settles off the coast of Southern California.

Daytime heating over the mountains of the western United States plays a major role in the development and evolution of the monsoon.

Where does the NAM impact?

A typical monsoon pattern has the greatest impact in Arizona, New Mexico, and Colorado. This can vary from year-to-year, depending on the strength and duration of the monsoon pattern.

What typically occurs during the NAM?

Depending on the location, heavy rain, flash flooding, dust storms, and abundant lightning strikes typically occur during the North American Monsoon.

Why do we care about the NAM as outdoor enthusiasts?

Whether you're a biker, climber, hiker, or a rafting guide, it is important to understand that the monsoon brings higher chances of lightning (from the alpine all the way down to the valley floors) and also heavy rain that can lead to flooding.

A good rule of thumb is to start your high alpine hikes very early in the morning and plan to be below treeline by 12 PM.

Because weather patterns change each day, be mindful that the risk of lightning can occur earlier than noon on some days, and on other days, the risk of thunderstorms could hold off until later in the afternoon.

Check the hourly forecasts here on OpenSummit to always be prepared with the latest weather information for your outdoor adventures.

RELATED: How To Read Clouds Above Treeline

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