Peter Sinks, located high in the Bear River Range of Utah’s Cache County, is consistently recognized as one of the coldest reliably measured places in the contiguous United States. Situated about 20 miles northeast of Logan, its extreme temperatures often rival those found much farther north in Alaska or Canada. The area’s notoriety stems from readings that have nearly matched the all-time low temperature record for the Lower 48 states. This extreme environment results from a combination of high elevation, dry air, and a unique land formation.
The Unique Topography of Peter Sinks
The physical geography of Peter Sinks is the foundational element enabling its intense cold. The location is a karstic depression, or doline, a type of sinkhole formed in the underlying limestone rock of the Bear River Mountains. This geological structure creates a massive, natural bowl surrounded by high ridges.
The basin is elongated, measuring about two miles long and half a mile wide, with its floor sitting over 8,100 feet above sea level. Crucially, the depression has no natural surface outlet to drain air or water, acting as a sealed container. The surrounding ridges rise hundreds of feet above the basin floor, creating a deep pocket that effectively traps the atmosphere below.
The Meteorological Process of Cold Air Pooling
The extreme cold at Peter Sinks is caused by a phenomenon known as cold air pooling. This process begins on clear, calm nights when the atmosphere is stable and winds are minimal. The ground, especially when covered with snow, rapidly loses heat to space through radiative cooling.
As the air near the ground cools, it becomes denser and heavier than the surrounding warmer air. This dense, cold air then flows downslope from the surrounding ridges into the basin below, a process known as katabatic flow. Because the depression is a closed bowl, the cold air collects on the floor, much like water pooling in a container.
This continuous influx of cold air creates a strong thermal inversion, meaning the air temperature increases with height above the basin floor. The trapped layer of cold air cannot mix with the warmer air mass above the rim, allowing it to continue cooling, often by as much as 70 degrees Fahrenheit compared to the air just outside the basin. This process continues until the cold air “lake” fills the basin up to the lowest point of the surrounding ridge, at which point excess air may spill over.
Measuring and Validating Extreme Temperatures
The extreme temperatures recorded at Peter Sinks are consistently monitored and verified by specialized equipment. The official record for the area is -69.3 degrees Fahrenheit, recorded on February 1, 1985. This reading is the second-coldest temperature ever verified in the contiguous United States, falling just 0.4 degrees short of the national record.
Data collection is performed by sophisticated remote weather stations, often managed by institutions like the Utah State University Climate Center. Verification of the 1985 record involved automated instrumentation and calibrated alcohol thermometers, since mercury freezes at much higher temperatures. The thermometer used to capture the record was later sent to the U.S. Bureau of Standards for confirmation, lending high credibility to the measurement.