Thick ice

Ice fishermen at frigid Antero Reservoir have some work to do before dropping a line. (Photo courtesy Getty Images)

Some locations in Colorado have a knack for posting bone-chilling thermometer readings this time of year, and one such location is Park County’s own Antero Reservoir.

On the morning of Dec. 30, for example, the temperature plummeted to -50 degrees to make Antero Reservoir the coldest location in the Lower 48 for the day. The -50 recorded that day also represents the coldest temperature registered in the Lower 48 thus far this winter.

That temperature was also the fourth-coldest at Antero Reservoir since records began being kept there in 1961. The coldest temperature ever recorded at Antero Reservoir was -54 in 1962.

Only Birch Creek, Alaska, which recorded the lowest temperature this winter in the entire United States at -51 degrees Dec. 17, can boast a lower number than Antero Reservoir posted Monday morning ... by one degree.

But none of these icy facts represent anything unusual for Antero Reservoir.

In 2019, temperature readings of -49 were recorded at the reservoir on two consecutive days, Dec. 30 and Dec. 31. Antero had the distinct honor of recording the lowest temperatures in the Lower 48 on each of those days as well. Antero also reported a low of -51 degrees Dec. 22, 2015.

These instances of extreme cold beg the question: Why do mercury levels at Antero Reservoir dip so low on such a regular basis?

According to meteorologists, several locations in Colorado are nestled within mountain ranges where cold air settles and is trapped throughout the winter months. The crux of the phenomenon is that cold air settles while hot air rises, due to cold air being more dense than warm air. Layers of cold air that settle in these locations are kept in place for extended periods due in large part to the mountainous terrain that surrounds them.

Antero Reservoir is situated in a central portion of an expansive bowl-shaped valley surrounded by mountains, and sits at a lofty elevation of 8,942 feet above sea level; perfect circumstances for producing extremely cold temperatures this time of year.

Additionally, perfect conditions – low winds, clear skies and a solid snow cover – combined to produce excessively low temperatures across the entire area Dec. 30, according to numerous local meteorologists. Many locations within the county reached sub-zero temperatures that morning, but none approached those observed at Antero Reservoir.

Other similarly situated Colorado communities that regularly boast some of the state’s coldest temperatures include Craig, Gunnison and Alamosa, to name a few.

The word “Antero” is derived from the Spanish word “first,” as it was the first dam on the South Platte River near the river’s origin.

Originally built in 1909, this earth-fill dam is believed to occupy the site of a former lakebed, probably no more than 300 years old. Green Lake is submerged within Antero Reservoir.

In addition to record-setting thermometer readings, Antero is also renowned for its trophy-sized brown and rainbow trout and is considered one of the nation’s premiere freshwater fisheries.

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