Colorado Water Year Ended as Hottest Ever Recorded

The Colorado Water Year just closed as the hottest ever recorded, and the numbers behind it are stark. The state climate office released its annual water-year report on October 20, covering the twelve months from October 2025 through September 2026, and it found a season of superlatives: the warmest temperatures in the historical record, the worst snowpack in history, and reservoirs sitting at their lowest levels since the drought year of 2002.

Climatologists use the water-year calendar, which runs October through September, because it follows the natural movement of water from snowfall through spring runoff. This year, that movement broke down almost from the start. Temperatures ran above average on nearly four out of every five days of the year, according to the report, and the heat came with a lack of precipitation that left rivers, farms, and cities strained across the state.

A year of heat with no precedent

The most striking finding was the sheer scale of the warmth. Statewide temperatures finished the water year four and a half degrees Fahrenheit above the 1991 to 2020 average, roughly two degrees warmer than the next-hottest water year on record, which came in 1934 during the Dust Bowl era. On a longer timeline, the report notes that Colorado averaged about six degrees hotter over these twelve months than across the entire twentieth century.

The heat was relentless rather than episodic. More than half of the water year's days ran at least five degrees warmer than normal, and more than a quarter soared into double digits above the norm. December, February, March, and August each set new all-time monthly heat records, while July and September logged their second-hottest averages. The state endured seven distinct heat waves, two more than Colorado has ever recorded in a single year.

"It was ridiculously warm," Allie Mazurek, an engagement climatologist at the state climate office, told Rocky Mountain PBS. "This water year far outdid anything else that we've seen in recorded history for Colorado. It wasn't just our warmest on record, it was warmest on record by a substantial margin."

Yet Mazurek pushed back on treating the season as a new baseline. She noted that while the state's climate has been steadily warming for decades, this year should still stand out even looking decades ahead, a rare extreme rather than the new normal. The report also tallied warm and cool daily records, finding more than twenty times as many daily warm records as cool ones, the most lopsided ratio ever observed, according to a separate rundown of the data by Aspen Journalism's water desk.

The snowpack that never came

While temperatures soared, precipitation lagged. The Colorado Water Year ranks as the eighteenth-driest in the state's history on paper, but that ranking hides an important wrinkle. A massive flood event struck southwest Colorado in October 2025, when areas near Pagosa Springs and Durango received more than nine inches of rain in a single week, and a very wet September on the southeastern plains also padded the totals. Strip out that opening flood and the year falls to the sixth-driest overall.

Those rainstorms did little for the water supply that matters most. In Colorado, snowpack is the savings account of the water system: snow stays on the ground through winter and melts slowly into rivers and reservoirs each spring. The snow simply never accumulated this year. The first quarter of 2026 ranked as the fourth-driest on record, and March ran nearly ten degrees warmer than normal, melting what little snow existed. The statewide snowpack peaked at barely half of average in early March, about a month ahead of schedule, and the season's snow water content finished as the worst ever measured.

The state's former climatologist has a saying that "snow is well-behaved," meaning it remains in place and filters gradually into streams, and this year proved the point in reverse. Runoff peaked far ahead of normal, and stream flows shrank through the summer, with Colorado River flows near Cameo dropping to their lowest ever recorded during the warm months.

What residents actually felt

The consequences touched nearly every corner of the state. Ranchers struggled to feed their cattle on withered range. River guides adjusted operations for low flows. Skiers found patchy slopes and poor conditions, and ski areas in the San Juan Mountains were forced to close early or run spring guests on thin strips of slush. Growers of the state's famous green chile reported the worst season they had ever seen, and reservoir levels dropped low enough to curtail boating and other recreation.

Cities responded with restrictions. Many municipalities limited lawn watering all summer, and Denver's water utility went further, banning outdoor watering outright after October first and threatening a five-hundred-dollar penalty for first violations. A report from 9News found the utility had already issued one hundred seventy-five thousand dollars in fines through mid-October, according to the station's tally cited by the outlet.

The state's largest reservoirs are drained near historic lows. Blue Mesa, the biggest in Colorado, sat at just sixteen percent of capacity as of this week, while Lake Dillon, the main reservoir supplying Denver, held roughly two-thirds of its normal volume. Reservoir levels have not been this low since 2002, the driest water year in the recorded record. On Tuesday, more than half the state remained in severe drought or worse, and parts of Garfield and Pitkin counties, home to Aspen and Glenwood Springs, have spent fifteen consecutive months in extreme or exceptional drought. Downstream, Lake Mead and Lake Powell remain near record lows while western states continue negotiating over the dwindling river.

"Everybody felt the effects of these temperatures and the lack of precipitation in some way or another," Mazurek said.

What a record El Nino could bring

Attention now turns to a strong El Nino pattern that has formed over the Pacific and could shape Colorado's winter. The connection is murky, however: the state sits in the middle of the zones where the pattern typically expresses itself, so its effects on local precipitation are hard to predict. State climatologist Russ Schumacher tempered expectations in a recent interview, saying there is reason for cautious optimism about a decent winter but that it remains too early to tell.

The national winter outlook gives the southern mountains of Colorado an above-average chance of wetter-than-normal conditions, with the northern mountains rated as equal odds for above or below normal. Even a generous winter would not erase the damage, though. Mazurek noted that it would be hard to repeat something this extreme two years in a row, but added that even an average snowpack would not refill reservoirs drained to historic lows. For a state that just watched the Colorado Water Year set records in all the wrong ways, the recovery is measured in years, not storms. Readers can compare this regional picture with the global one in the 2026 State of the Climate report, which found seven of sixteen planetary vital signs at record extremes, or see how another country is coping in New Zealand's latest national climate assessment.