When does Monsoon season start? What causes Monsoon?

The official start date of the Arizona Monsoon season is June 15.  In 2008, the National Weather Service determined the AZ Monsoon starting date along with the ending date of September 30.

Tucson Phoenix Monsoon weather
storm clouds Monsoon season

What causes monsoon?

Traders sailing the Indian Ocean and Arabian Sea used the word monsoon to describe a system of alternating winds which blow from the northeast during the northern winter and from the southwest, during the northern summer. Therefore, the term monsoon refers solely to a seasonal wind shift, and not precipitation.

Mexican monsoon cloud
Arizona Mexico Border storm clouds

Arizona happens to be located in the area of the United States that experiences a monsoonal circulation. During the summer months, winds shift from a west or northwest direction to a south or southeasterly direction.

Monsoon weather for Arizona
Microburst clouds during Monsoon

This wind shift allows moisture from the Gulf of California and the Gulf of Mexico to stream into Arizona.  A monsoonal circulation produces a radical change in moisture conditions throughout the entire state.

Arizona thunderstorm dark clouds
Monsoon storm clouds over Coronado Mountains

Thunderstorm or cumulonimbus clouds are very familiar during monsoon season.  These storm clouds cause lightning, hail and heavy rain.

Arizona desert Monsoon Storms
dark thunderstorm burst clouds

What Arizona experiences during the summer months is only a small part of a larger circulation that encompasses much of the southwestern United States and northwestern Mexico. Thus, it sometimes is also known as the Mexican monsoon. The National Weather Service calls it the North American Monsoon.

microburst monsoon storm cloud
Monsoon clouds Mexican Arizona Border

This adjustment in wind direction is the result of two meteorological changes:

  1. the movement northward of the huge upper level subtropical high pressure system, known as the Bermuda High,
  2. and the intense heating of the Mohave Desert creating rising air and surface low pressure, called a thermal low
severe dark thunderstorm cumulus cloud
Monsoon Storm clouds on top of mountains

The southerly low-level winds help to bring in moisture from Mexico. When this moisture encounters the higher terrain of Arizona mountain ranges, it gets lifted and forms thunderstorms.

dark storm Clouds on arizona border
Monsoon storm Coronado Mountains

Small driving factors such as: atmosphere interaction, land elevation, soil moisture and vegetation all play a part in what drives the Arizona Monsoon; but it is also why predicting storm intensity is so difficult.

When such high volume rain descends upon the Arizona desert the ground and the surface streets flood. Quite often the rain pools on streets during monsoon storms causing dangerous driving conditions.

cumulus thunderstorm cloud
Storm burst clouds at Arizona Mexico Border

The monsoon circulation does not produce thunderstorms every day during the summer months, but rather monsoon storms occur in a pattern known as “bursts” and “breaks”.

best Microburst storm cloud photo
Monsoon microburst cumulus cloud

This cycle of bursts and breaks will continue from the onset of the monsoon (typically June), until the time when cold fronts begin to move across the state of Arizona (typically September), which will return our winds to a westerly or northwesterly direction.

We hope you enjoyed this article.  Our goal was to make Monsoon Season easier to understand.

Coronado National Memorial in the Huachuca Mountain range of the Coronado National Forest, Arizona

We drove to Coronado National Monument from Tucson through Fort Huachuca.  The Huachuca Mountain range is part of the Coronado National Forest. The Huachuca Mountain area is owned mainly by the USDA Forest Service and the United States Army, Fort Huachuca. 

The Coronado National Forest covers 1,780,000 acres of southeastern Arizona and southwestern New Mexico. Elevations range from 3000 feet to 10,720 feet in twelve widely scattered mountain ranges or sky islands.  

What is a sky island?   A mountain that rises high from the desert floor and has a different ecosystem than the lowlands that surround it. Hence, two dramatically different environments.

Coronado Forest Arizona
Entrance to the Coronado National Memorial

You can see the beautiful landscape along the Mexico and Arizona Border at the  Coronado National Memorial on the south end of the Huachuca Mountains.  This living memorial is composed of over 4,700 acres and commemorates the first major exploration of the American Southwest by Europeans.

There is a visitors center down Coronado Memorial Road about 5 miles from Hwy. 92 with local history and exhibits.  It is open everyday except Thanksgiving and Christmas.

Visitors Center at Coronado
Coronado National Forest Ranger Station

The rangers at the Coronado National Monument visitor’s center were friendly and  knowledgeable.  For a fun picture be sure to try on the mail armor, conquistador helmet and the sword.

The ranger recommended that we drive up to Montezuma Pass Overlook.

Coronado National Memorial Arizona
Montezuma Peak at Coronado National Memorial Park

Just passed the visitor’s center is Montezuma Peak at 7,676 elevation.  Montezuma Peak is the most prominent peak at Coronado National Memorial area.

The road up to Montezuma Pass Overlook turns to an unpaved, rough dirt road.  There are several switchbacks as it winds up the mountain.  A bit scary on some of the turns but well worth the drive as the views are spectacular from the Overlook.

San Pedro Valley
switchbacks up to Coronado Peak – view of the San Pedro Valley
Coronado National Forest Map
Map of Coronado National Monument Park, Hauchuca Mountains

The Yaqui Ridge Trail down to the Arizona – Mexican border is a nice little side trip that is all downhill.

San Pedro Valley
Coronado Peak facing Mexico and overlooking the San Pedro Valley

There are picnic tables and restrooms at the Montezuma Pass Overlook.  This is also where you will pickup the trail to Coronado Peak.

Coronado National Memorial was named in honor of Spanish conquistador Francisco Vásquez de Coronado.  In 1939 the House Committee on Foreign Affairs stated,  “this was one of the greatest land expeditions the world has known, a new civilization was established in the great American Southwest.”

San Pedro Valley
San Pedro Valley

Coronado Peak Trail starts at the Overlook.  This short hiking trail climbs from 6,575 to 6,864 feet in elevation, and culminates in panoramic views from Coronado Peak.

Coronado Peak overlook
Montezuma Pass Overlook at Coronado National Monument – viewing South towards Mexico
Miller Peak Huachuca Mountains
Miller Peak Wilderness in Coronado National Forest

The photo above is a perfect view of Miller Peak, elevation 9,466 ft., in the Coronado National Memorial.  Trails climb from all sides of the range to Miller Peak Wilderness in the Huachuca Mountains.

Montezuma  Canyon Road
Century Plant Agave on Montezuma Canyon Road

Driving down Montezuma Canyon Road, we took a picture of a healthy Century Plant Agave, some say agave cactus.

Planning a trip to Coronado National Monument in southern Arizona?  Here is the link to the Visitor’s Center http://www.nps.gov/coro/planyourvisit/visitorcenters.htm