Colorado water year 2025 summary

Bruce Bartleson

The following excerpts were recently published by Colorado State climatologist Russ Schumacher and are full of good information. The water year (WY), which runs from October 1 through the end of September, is commonly used in climatological and hydrological discussions. It more accurately reflects how water naturally moves through the environment without mixing up precipitation patterns, in contrast to the calendar year.

Here is a summary of some of that information:

Temperatures

“WY 2025 started out with record-setting warmth, with October 2024 ranking as the hottest October on record for the state,” Schumacher wrote. “Late fall and early winter featured a mixed bag of temperature anomalies. November 2024 and January 2025 ranked below average, sandwiching a very warm December (the 3rd warmest on record). From February onward, every other month in WY 2025 finished above average (except for May, which was near average). 

Spatially, the above average temperatures were realized in nearly every part of the state, though the most significant warmth occurred in northeast, western and south-central Colorado. A few locations on the Western Slope saw their warmest water year on record.”  

Some parts of the state showed some marked trends. For example, Grand Junction had 81 days of 90 degree temperatures compared to their last 30 years average of 68 days. Cortez had 64 days of 90 degree temperatures compared to their 30 year average of 41 days and Fort Collins had 42 days compared to their 30 year average of 30 days. Gunnison had zero 90 degree days as I recently discussed in the Sept. 8 edition of the Times.

Precipitation

According to Schumacher, WY 2025 finished near-average in terms of precipitation, ranking as the 51st driest in the 130-year record. The last water year that was drier than WY 2025 was WY 2022. Statewide, most months in WY 2025 do not stand out as particularly noteworthy, though there were a few exceptions. November 2024, which featured a record-breaking snowstorm that affected most of the state, finished as the 5th wettest on record. That abnormally wet month was followed by a much drier December — the 9th driest on record. 

Perhaps the biggest story surrounding precipitation during WY 2025 was that conditions were very different depending on which side of the Continental Divide you were on. Much of the Western Slope saw a top-10 dry water year, while a few locations on the Eastern Plains saw a top-10 wettest year. These precipitation patterns also led to variability in drought conditions.

Notable events

Schumacher concludes with the following: “Practically everywhere in the state recorded unusually warm December temperatures … except for Gunnison. They stayed below average for the first several weeks of December. What was the cause of this strange cold signal? Blame it all on geography and snow cover.”  

We all know what happened here in Gunnison — it snowed something like a foot the day before Thanksgiving and that reflected all the sun’s heat back out to the atmosphere. Our topography, being in a bowl, kept the cold air trapped and radiant heat loss made it colder.

The full report is available from Schumacher by emailing russ.schumacher@colostate.edu. 

(Bruce Bartleson is a retired emeritus professor of geology at Western Colorado University. He spends most of his time now watching the weather.)