Peter Sinks is a high-elevation sinkhole in Utah’s Bear River Mountains and one of the coldest places in the contiguous United States. Its enclosed basin traps dense cold air on clear, calm nights, creating extreme temperature inversions and a basin floor so harsh that trees cannot grow there and summer freezes remain common. Formed by karst processes in limestone and dolomite, it is one of several nearby collapse depressions shaped with help from faulting and erosion. Research beginning in the early 1980s established its meteorological importance, and a February 1, 1985, reading of -69.3 °F set Utah’s record low and ranked second-lowest in the contiguous United States.