The frequent showers and afternoon thunderstorms that come along with monsoon season in Colorado often ramp up in July, on average, and some meteorologists say there’s a possibility that this year’s seasonal pattern could result in above-average rainfall and thunderstorm activity in the region. 

After above-normal precipitation fell across Colorado’s Rocky Mountains last summer and reservoirs began to fill-and-spill this spring thanks to an above-normal snow year, most regions of the state are drought free currently. 

The National Weather Service’s Climate Prediction Center recently announced that this summer should experience a shift from El Nino to La Nina conditions, and while there’s no direct tie between either of these two weather patterns and an active monsoon season, OpenSnow meteorologist Alan Smith says La Nina typically “tips the odds in favor of a stronger monsoon,” according to a report posted on June 29. 

“The strength and duration of the monsoon varies from year to year and is challenging to predict in advance,” Smith wrote. “However, there are some signs that 2024 could be an active monsoon season.”

The National Weather Service’s Albuquerque Weather Forecast Office issued a report that stated, “Promises of a La Nina spell great news for the North American Monsoon this year.” Meteorologists from the office say often the shift results in a weaker subtropical jet stream and less dry air pockets that move in from the west and northwest. 

Smith says the subtropical jet stream plays a vital role in monsoon season, so if the conditions ultimately set up, it could spell good news for the region. 

The switch to La Nina is expected to hit around July or August, according to the National Weather Service. 

“We examined past years dating back to 1990 in which La Nina conditions were present in either July or August (or both),” Alan Smith wrote. “Of these 11 years, we found that above-average rainfall is favored in Arizona, Utah, Western Colorado, and Western New Mexico.”

Smith also notes that stronger-than-normal high pressure centers and earlier-than-normal northward progressions tend to bring about more intense monsoon seasons. He said a hot June usually results from stronger-than-usual high pressure that can also help feed the monsoon. 

“This is exactly what we have seen in June 2024,” he wrote in his blog post. “The average position of the subtropical high has been located further north than usual for this early in the summer, and the Southwest has been much hotter than average this month.”

Warming water temperatures in the Pacific Ocean can also influence how much it rains in Colorado, and Smith says the likelihood of significant moisture surges increases when ocean temperatures reach 29 degrees celsius. As of June 27, water temperatures in the Gulf of California were in the upper 25-30 degrees celsius range.  

While Smith painted an optimistic prediction for this year’s monsoon, he also noted that things can change. 

“Keep in mind that there is an inherent degree of uncertainty when it comes to monsoon season forecasts,” he said. 

Weather.com senior meteorologist Chris Dolce’s prediction published on June 14 called for a drier than normal monsoon season. The Climate Prediction Center’s long-term forecasts call for above average precipitation in its three-to-four week outlook but then expects precipitation to fall below normal in its three-month outlook for the mountainous areas of Colorado. 

For more information on weather outlooks and the latest climate-related coverage, visit Weather.gov/bou or OpenSnow.com/news.