Utah's temperatures vary greatly with changing altitude and latitude. The mountains and elevated valleys have the cooler climates, while lower areas of the state have higher temperatures.
Generally, there is about a 5F., decrease in temperature for each 1,000 feet increase in altitude, and approximately one degree decrease in average yearly temperature for each one degree of increase in latitude. Thus, equivalent areas in the southern counties of the state generally experience average annual temperatures two to four degrees F., warmer than those at similar altitude in the extreme northern part of the state. However, there are several exceptions to these generalities, because strong temperature inversions periodically affect many Utah valleys and humidities often differ significantly from one season to another.
Temperatures above 100F., occur during most summer seasons in many of the lower valleys of the state. The low humidity makes these high temperatures and hot sunshine more bearable in Utah than in the more humid regions of the country. The low humidity also enables evaporative "swamp" coolers to operate very efficiently.
The highest official maximum temperature ever recorded in Utah was 117F, observed on July 5, 1985, at St. George in southwestern Utah. The warmest thermometer reading ever for Salt Lake City was 107F., on July 26, 1960.
Sub-zero temperatures occur during most winters in all but the warmest (or southernmost) areas of the state. However, prolonged periods of extremely cold weather are infrequent. Most climatic data show that January is generally the coldest month of the year.
The lowest official minimum temperature ever recorded in Utah was -69F., recorded on February 1, 1985, in uninhabited Peter Sinks at the top of Logan Canyon. The lowest temperature ever recorded in an inhabited area of Utah was -50F., observed on February 6, 1899, at Woodruff.
Much of the information for this section originally appeared in the copyrighted book Utah's Weather and Climate, edited by Dan Pope and Clayton Brough, in 1996. UCCW Directors have received permission from the copyright owners of this book to reproduce such information on its website and to revise and updated it where appropriate.