An unprecedented heat wave over the last few days has shattered temperature records across Colorado — and may have forced the state’s record-low snowpack to peak weeks ahead of schedule.
In a normal year, the state’s snowpack reaches its highest levels in early April, according to data collected by the U.S. Department of Agriculture (USDA). After that, the water stored as mountain snow steadily drains away, with most of it gone by late June or early July.
Colorado hasn’t stuck to the script this year. Anyone who’s visited the state’s high country has seen the snowless mountainsides, left bare by a season of warm weather and low precipitation. As of mid-March, the state faced its worst snowpack in the 41-year history of the USDA snow monitoring program, known as SNOTEL.
Forecasts don’t predict a significant spring snowstorm within the next few weeks, either. That means as ski slopes and alpine drifts melt into slush, snow levels may have already hit a high-water mark on March 9, roughly a month early.
“That really sets you up poorly for the year to come in terms of water supply,” said Peter Goble, Colorado’s assistant state climatologist at the Colorado Climate Center. “You not only have less water, but you have to stretch it out longer than if the weather had stayed colder longer.”
The early melt also likely offers a preview of Colorado’s hotter future. A 2024 report from the Colorado Climate Center found spring snowpack has shrunk in the last 75 years, but scientists only have modest confidence that the trend will continue. It’s a far better bet that snowpack will peak earlier, creating new challenges for the state’s water managers and its ecosystems.
‘Mother nature’s drip irrigation system’
Snowpack is crucial to water supplies because it acts as a sort of natural reservoir.
After falling in solid form, snow melts gradually through the spring and summer, providing a reliable water source for urban communities and farmers. A steady trickle from the snowpack also delays the arrival of the fire season and sustains countless plants and animals.
Noah Molotch, a professor of geography at the University of Colorado Boulder, thinks about snowmelt as a drip irrigation network for the Western U.S. The runoff provides a steady, reliable water source. The earlier the system turns on, however, the earlier it will probably turn off, leaving places dependent on rainfall for moisture during the hottest parts of the year.
“Even if it’s a relatively small average change in timing, it can pile onto the other challenges we face with regard to climate warming,” Molotch said.
Early snowmelt creates a “triple whammy” of interconnected issues, he said.
Part of the challenge is that when the snow melts sooner, less liquid water makes it into streams and rivers. The dynamic occurs due to the cooler conditions and shorter days in the early spring. When snowpack melts more slowly, it has more time to absorb into the soil and evaporate rather than reaching waterways.
Molotch compares the phenomenon to watering a houseplant. If you pour quickly, more water pools into the tray beneath the pot, and might even spill all over the floor. That’s why, in a natural landscape, quicker runoff later in the year helps ensure fuller waterways.
Early runoff also lengthens the dry season in the spring and summer, opening the window for wildfires. While vegetation growth, rainfall, and other factors play a role in fire risk, early runoff primes mountain landscapes for blazes, Molotch said.
In addition, it creates headaches for water managers, who have to leave room in reservoirs in anticipation of precipitation events. As a result, it’s difficult to store early runoff without increasing flooding risks.
Water restrictions ahead
Challenges related to shifting snowmelt would persist in years with normal or above-average snowpack.
This year, however, the early runoff would end a remarkably dry winter season across Colorado. In addition to federal SNOTEL stations, Molotch assists with a separate project for the U.S. Bureau of Reclamation to estimate snowpack based on satellite data.
Its latest weekly report shows snowpack in the Southern Rockies region — which includes Colorado’s major river basins — is currently at 38% of average for the data spanning the last 26 years. Those conditions also follow a below-average snowpack year for the winter spanning 2024 and 2025.
“Reservoirs may already be depleted when we're faced with this additional water deficit from the current snow drought,” Molotch said. “And that’s all just within the state of Colorado.” The situation has set the table for strict water usage limits in the months ahead. Gov. Jared Polis has activated the Colorado Drought Task Force, shifting the state towards an official drought declaration. Denver Water is also set to implement watering restrictions due to low snowpack starting on March 25.
