After years of unpredictable monsoon seasons, meteorologists are forecasting a wetter-than-average summer and early fall across Arizona, raising the potential for more frequent heavy rain, flash flooding and severe thunderstorms.
The outlook was presented Monday during the annual North American Monsoon Outlook lecture, now in its 15th year, which examined long-term weather patterns and conditions leading into Arizona's 2026 monsoon season.
Forecasters expect this year's monsoon to produce above-average rainfall, particularly during the core months of July and August and into the transition period in September and October.
Several atmospheric conditions are aligning to support a more active season, including an unusually dry winter, below-average snowpack in the Colorado River Basin, warming waters in the northern Gulf of California and the development of El Niño in the Pacific Ocean.
Meteorologists say those factors should create favorable conditions for stronger moisture flow into Arizona and increase the likelihood of thunderstorms throughout the state.
"This has the potential to be one of the wetter monsoon seasons of the 21st century," said Daniel Henz with the Flood Control District of Maricopa County.
The forecast draws comparisons to 2018, a year that also followed a dry winter and featured an active eastern Pacific hurricane season. That year culminated with Hurricane Rosa, which produced widespread flooding across Arizona after delivering several inches of rain in a single day in some locations.
Early season may remain hot
Despite the optimistic rainfall outlook, forecasters cautioned that the beginning of the monsoon season could remain deceptively dry.
“There should be some type of ramp that starts late summer into the fall tropical activity,” said Jonny Maloy, meteorologist. “If a strong area of high pressure settles over Arizona during early July, it could suppress thunderstorm development and prolong extreme heat before more favorable weather patterns emerge later in the season.”
That scenario could resemble 2024, when a persistent heat dome limited thunderstorm activity across much of the summer.
Meteorologists stressed that a delayed start would not necessarily indicate a failed monsoon, noting that many wet years receive much of their rainfall during August, September and even October.
Flooding remains the greatest concern
With expectations for increased rainfall comes a heightened flood threat.
Heavy rain events capable of producing roadway flooding and dangerous washes are expected to occur more frequently than average. Forecasters anticipate more than 50 heavy rain days across the region's rain gauge network this season, along with more than two dozen significant rainfall events capable of producing localized flooding.
Officials reminded residents that just six inches of moving water can knock a person off their feet, while approximately 18 inches can carry away most vehicles.
Strong thunderstorm outflow winds, blowing dust, dangerous lightning and extreme humidity will also accompany many storms.
Rainfall critical for Arizona
The North American monsoon typically provides between 30% and 40% of Arizona's annual precipitation, making it one of the state's most important weather seasons.
While rainfall totals vary dramatically from year to year, meteorologists said the combination of current climate indicators points toward an active season for much of central and southern Arizona.
Forecast confidence is expected to improve as the season progresses. Meteorologists said they can generally identify potential storm outbreaks three to seven days in advance, with much higher confidence arriving one to two days before major weather events.
Residents are encouraged to monitor forecasts throughout the summer and remain prepared for rapidly changing weather, especially during periods of heavy rain, dust storms and flash flooding.
