With Dillon experiencing its second-warmest December on record, Denver Water estimates the Dillon Reservoir will not freeze over until the end of January.

Jimmy Luthye, the senior media relations coordinator at Denver Water, wrote in an email that warm temperatures are “really the driver” behind the reservoir not yet being frozen, although high winds in late December also played a role. 

“When coupled with the heat, that much wind hinders the freezing process,” Luthye wrote. “Of course, if the temperatures were colder, that wouldn’t be the case.”

Current conditions and forecasts, Luthye wrote, show the reservoir likely will not freeze over “until closer to the end of January.”

Based on data starting in 1966, the reservoir has, on average, frozen over Dec. 25. The reservoir has frozen on or after Jan. 1 only 13 times in the 59 years on record, but seven of those years have been since 2010 and three have been in the last four years. When the reservoir freezes this year, it will be the 14th instance and the fourth in five years.

In the winter of 2024-2025, the reservoir froze over Jan. 9, the same date it froze over the year prior. The latest reservoir freeze on record occurred in 1980, when it froze over on Jan. 31, 1981. That year also featured the hottest December on record in Dillon, according to data that goes back to 1910.

If the reservoir freezes toward the end of January, it will be the third time since 1966 it will have frozen in the second half of January, joining the Jan. 31, 1981, and Jan. 24, 2014, freezes.

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December 2025 included 25 days with an average temperature above normal, Luthye wrote. The average temperature, which was just under 28 degrees Fahrenheit, was nearly 11 degrees warmer than the average December temperature in Dillon from 1910-2025. Luthye added that the low temperature Dec. 20 was the warmest low temperature on record at 35 degrees.

The earliest the reservoir has frozen over on record was in 1972, when it froze Dec. 10.

When the Dillon Reservoir freezes, it provides recreation opportunities for residents and visitors, including cross-country skiing, ice fishing, ice skating and snow kiting. 

The town of Dillon grooms its lake loops, or multi-use tracks, on the lake when it freezes, giving people a place to cross-country ski, snowshoe or fat bike. The town has maintained a community ice rink and hosted dog sled races on the lake in years past as well. Town manager Nathan Johnson wrote in an email that the town will prioritize the lake loops this year and that the timing of the lake freezing and ice safety conditions will dictate whether it has an ice rink this winter.