Historical Trends of Record Daily Temperatures at Denver, Colorado, 1872-2010

The local National Weather Service Weather Forecast Office maintains a compilation of the record temperatures for Denver, Colorado, for each calendar day, along with the year in which each record was set. The data span the period of 1872-2010. The daily record high and low (maximum and minimum) temperature data are examined with regard to the years in which the standing records were set. Analysis shows that far more daily record-high temperatures have been broken recently than record-low temperatures. This lopsided trend began at the end of the 1970s and accelerated through the last three decades. In the most recent decade of 2001-2010 new record-breaking high temperatures outnumbered new record lows by a ratio of 2.6 to 1. This evidence indicates that climate of the Denver area has been warming, at least since the 1970s. Although the measurement site moved substantially in 1995 from Stapleton Airport to Denver International Airport, comparisons of simultaneous temperatures at these two sites show that site relocation is not a plausible explanation for the observed recent disparate trend in record temperatures.