Tucson experienced below average rainfall in July — typically an active month for the monsoon — but there is still hope for August and September, according to local weather experts.

Consistent with predictions the monsoon would come late this year, July officially brought about an inch of rain — a good portion of that falling Wednesday afternoon — which is low compared to the normal 2.25 inches recorded during the month.

Tucson’s monsoon runs from mid-June to the end of September; an average season is about 6 inches of rain.

“It really comes down to the fact that the high-pressure system that draws up most of our moisture to get these storms initiated hasn’t really had an easy time sticking to its most favorable position,” said National Weather Service meteorologist Maddie Powell. “It’s been shifting a lot and any little variation in where that high sits can mean the difference between a busy day and a non-busy day as far as rain goes.”

According to Powell, the Southwest typically sees a seasonal shift from a low-pressure system in the winter to a high-pressure system in the summer. The high-pressure system travels north toward the Four Corners region from Mexico, which causes the wind to shift and brings in moisture from the Gulf of California. This year, the high-pressure system is more active in its movement.

“It just comes down to where that high is, and part of that is just the lingering effects we had through the spring from El Niño, which didn’t really allow that high pressure to set up,” Powell said.

Earlier in the year, low-pressure systems stuck around longer and combined with El Niño weather conditions to create lower than normal temperatures and increased moisture through May. Because high-pressure systems depend on heat to push them north, Arizona’s cool spring is causing a delay in monsoon storms.

Although rainfall for the center of Tucson, which is recorded at the airport, is below normal, other areas of Tucson are experiencing plenty of rain.

“Rain events have been fewer and far between, but the variability is typical for this time of year,” said University of Arizona climatologist Mike Crimmins. “A lot of the storms have stuck to the mountains, but the middle of Tucson has been struggling.”

Heading into August, there’s still a chance that monsoon storms will increase, according to Crimmins.

The Tucson area has seen increased storm activity this week, including heavy downpours Wednesday that caused some washes to flow. Some areas of Tucson reported more than 2 inches of rain by Wednesday evening, particularly on the southeast side.

“I still think there’s plenty of time to catch up,” Crimmins said. “On average, August is the wettest month of the monsoon season, so there’s still opportunity for other parts of town to experience those storms.”

* I understand and agree that registration on or use of this site constitutes agreement to its user agreement and privacy policy.

The weather service said whether the rains pick up through August primarily depends on the high-pressure systems’ placement.

“It’s difficult to say that August is going to be a slam dunk or it’s not,” Powell said. “It’s kind of sitting in the equal-chances range, not above or below average as far as expected precipitation goes.”

According to Crimmins, there’s also a chance that Southern Arizona will experience higher rainfall in September as well, which could make up for its nearly dry July.

“The first two weeks of September are usually when the monsoons tail off, but this year there is the expectation that we’ll experience some tropical storm activity,” he said. “Since it’s been an active season, it’s definitely something we might contend with in September.”

Contact reporter Jasmine Demers at jdemers@tucson.com

Reporter

Jasmine joined the Star in 2019. With a master’s degree in journalism, Jasmine served in a variety of leadership roles, including The Daily Wildcat's editor-in-chief. She was also named Outstanding Newsperson of the Year by the UA School of Journalism.