Even though the calendar won’t mark the official start of autumn until Sept. 22, meteorological fall began on Labor Day. The shift means Colorado residents are now in the seasonal transition, and weather patterns are already starting to reflect it.
National Weather Service Meteorologist Russell Danielson said September will bring a mix of near-normal and slightly above-normal temperatures in metro Denver — with a few surprises.
“To begin, we'll see near-normal to slightly above-normal temperatures through Thursday, but then on Friday we have a strong cold front that comes through and highs may be in the low 70s, as well below normal,” he said. “Into the second week of September, we'll likely have above normal temperatures and we're looking for that to generally continue for much of the rest of the month.”
That means the cooler air at the end of this week may feel like a “fake fall.” Warmer weather will likely return before Denver settles into sustained 60- and 70-degree days next month.
When it comes to precipitation, Danielson said there are no big storms expected. “September is usually a pretty dry month for us, and there's no indication that it'll be either wetter or drier than average,” he said.
Average rainfall for the month of September in Denver is about 1.35 inches of rain. Should that prediction hold, it will follow an unusually soggy August. “It was the third rainiest August on record,” Danielson confirmed. Denver picked up 4.12 inches of rain last month, trailing only 1979, when 5.85 inches fell, and 1951, when 4.47 inches were recorded.
As for snow? “There's nothing on the horizon that looks like it'll bring snow to the Denver metro this month,” Danielson said. “The normal first snowfall for Denver is October 18th. And it is becoming quite rare to have a September snowfall, but the mountain regions do usually pick up some snowfall at higher elevations.”
Despite the wet August, drought remains a concern across Colorado, especially west of the Continental Divide.
“For the state of Colorado, it's a completely different story on the western slope to the eastern plains,” Danielson said. “There are dry conditions in the Denver metro, but nothing too bad. Now, the west of the continental divide on the western slope, there's extreme drought, which is the second-highest category for the majority of that area. Then, basically all of Rio Blanco and Garfield counties are in exceptional drought, which is the highest category.”
Those conditions, paired with September’s tendency for wind across the state, can heighten wildfire risk. “That extreme to exceptional drought is not a very good sign,” Danielson said. “People need to be very cautious about starting any fires, because while you think you may have put it out, perhaps some embers carry on and that may last a couple of days. All of a sudden, the wind picks up, with it being so dry, things can really, really ignite.”
Small showers and isolated thunderstorms are possible in the coming days in metro Denver. “Perhaps this weekend might be more of a widespread precipitation event, but it's still quite uncertain at this time,” Danielson said.
For now, Coloradans can expect September to bring a tease of fall weather, a return of heat, and average rainfall — with an eye on drought conditions out west that could continue to shape the fire season in the weeks ahead.
