![]() ![]() ![]() Since 2000, annual and spring precipitation totals have been generally below average. Precipitation varies widely from year to year. (Note that for Figures 5a and 5d, the average for individual reporting stations varies greatly because of the state’s large elevation range.) Colorado rarely experiences warm nights but has had an above average number in recent years. The horizontal black lines show the long-term (entire period) averages: (a) 1.3 nights, (b) 18.0 inches, (c) 5.3 inches, (d) 3.8 inches, (e) 1.8 days. Bars show averages over 5-year periods (last bar is a 6-year average). This storm also set a state record for lowest atmospheric sea level pressure (970.4 hPa) on March 13 in Lamar.įigure 5: Observed (a) annual number of warm nights (minimum temperature of 70☏ or higher), (b) total annual precipitation, (c) total spring (March–May) precipitation, (d) total fall (September–November) precipitation, and (e) annual number of 1-inch precipitation events (days with precipitation of 1 inch or more) for Colorado from (a, e) 1900 to 2020 and (b, c, d) 1895 to 2020. In March 2019, a “bomb cyclone” produced widespread blizzard conditions and record-high wind gusts and caused avalanches and major travel disruptions. Occasional blizzards can have significant impacts. ![]() Snowfall totals also vary across the state, with the high mountains receiving 150 inches to more than 400 inches per year. With the exception of the 2015–2020 period, Colorado has experienced mostly above average fall precipitation since 1980 (Figure 5d) and below average spring precipitation since 2000 (Figure 5c). Statewide, seasonal average precipitation has been variable. Seasonal patterns also vary: in the eastern plains and valleys, most precipitation falls during spring and summer, but the mountain peaks receive the most precipitation during the winter months. Local annual precipitation varies widely, from about 7 inches in the middle of the San Luis Valley to more than 60 inches in a few mountain locations. The driest consecutive 5-year interval was 1952–1956, and the wettest was 1995–1999. 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. ![]()
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