The driest multiyear periods were in the 1930s and 1950s, and the wettest were in the 1940s, 1980s, and 1990s (Figure 5b). Statewide total annual precipitation is 18.0 inches on average but has ranged from a low of 11.9 inches in 2002 to a high of 25.5 inches in 1941. A new state record for maximum temperature (115.0☏) was set at John Martin Dam on July 20, 2019. The greatest number of warm nights occurred in the 1930s, and in recent years, Colorado, along with other parts of the United States, has had an above average number of such nights (Figure 5a). Colorado rarely experiences warm nights due to its high elevation and generally dry climate. In addition to the overall trend of higher average temperatures, the number of very hot days has been above average since 2000 (Figure 3), and the number of very cold nights has been near or below average since 1990 (Figure 4). Six of the 8 warmest years on record for Colorado have occurred since 2012. The hottest year on record was 2012, with an average temperature of 48.3☏, which was 3.4☏ above the long-term average. Since 2000, the state has experienced the highest summer and spring average temperatures in the historical record (Figures 2a and 2b). Temperatures in Colorado have risen about 2.5☏ since the beginning of the 20th century (Figure 1) and have remained consistently higher than the long-term (1895–2020) average since 1998. Less warming is expected under a lower emissions future (the coldest end-of-century projections being about 2☏ warmer than the historical average green shading) and more warming under a higher emissions future (the hottest end-of-century projections being about 11☏ warmer than the hottest year in the historical record red shading). Historically unprecedented warming is projected during this century. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Shading indicates the range of annual temperatures from the set of models. Temperatures in Colorado (orange line) have risen about 2.5☏ since the beginning of the 20th century. Projected changes for 2006–2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions).

Figure 1: Observed and projected changes (compared to the 1901–1960 average) in near-surface air temperature for Colorado.

Denver precipitation totals 2021