Record-breaking temperatures in Dillon last month helped make for an unusually hot and dry July, but meteorologists expect monsoonal moisture will bring cooler temperatures and more frequent rain to Summit County and other Colorado mountain communities this week. 

The maximum temperature reached 87 degrees at the National Weather Service station in Dillon on both July 14 and July 21.

The July 14 temperature tied an 87-year-old record set in 1939, while the July 21 temperature tied a record set in 2005. 

Kenley Bonner, a meteorologist with the National Weather Service based in Boulder, said the Dillon station’s normal maximum temperature for July hovers around 75 degrees. The average temperature recorded last month was 80.8 degrees, she said. 

Maggie Ideker, also a meteorologist, said an upper-level area of high pressure over the Southwest contributed to the recent heat and arid conditions. High pressure tends to suppress cloud formation and precipitation, helping produce warm, dry weather. 

That high pressure system also disrupted the typical arrival of monsoon season in Colorado.

“Unfortunately, we had that area of high pressure that kind of slid back into the desert Southwest,” Ideker said. “So, all of the monsoon moisture that we should have been seeing got advected west and north of us.”

Now, the high pressure system has begun to shift east, allowing more moisture to shift from the southwest into Colorado. 

Monday, Aug. 10, and Tuesday, Aug. 11, are expected to remain relatively warm, with isolated to scattered afternoon showers and thunderstorms. By Wednesday, Ideker said, forecasters expect better moisture to move into the region, bringing more “numerous showers” across the region. 

“Thursday is really the best day that we’re expecting widespread showers and thunderstorms across the mountains and the plains,” Ideker said. 

The increased moisture could provide some relief from the recent dry conditions, but it also brings a combination of risks that will vary throughout the week. 

Lighting will remain a concern on Tuesday while some of the drier air lingers. Thunderstorms that produce little rain can still generate lightning capable of sparking wildfires. State wildfire officials have said the monsoonal weather will have little impact on wildfire danger. Summit County remains under “extreme” fire danger while ongoing Stage 2 fire restrictions prohibit all campfires.

“We’re still concerned about lightning and lightning-caused wildfires, but that rain will be very beneficial,” Ideker said. 

The heavier rainfall could also create localized flooding. Ideker said forecasters are watching for storms capable of producing high rainfall rates, though she said it’s too early to identify specific areas that may face greater flooding risk. 

Burn-scar areas are especially vulnerable to localized flooding, Ideker added, because the landscape can’t absorb as much water following a wildfire. 

For Summit County, daily chances of afternoon showers and thunderstorms will continue into the weekend. 

The Climate Prediction Center shows above-normal precipitation projected for western Colorado over the next three months. 

“We’re not quite in the middle of monsoon season yet, but we’re definitely approaching it,” Ideker said. “Cooler temperatures are on their way.”