By Chris Spears


DENVER (CBS4) – If you’ve been in Colorado for any length of time then you know that September doesn’t feel like it used to, at least not in recent years. The ninth month is known for mild days, cool nights, and occasionally a little bit of frost or light snow. Denver hasn’t recorded an accumulating September snow since the year 2000 when 0.2 inches fell at Stapleton.

Hot weather on Interstate 70 in Denver

(credit: CBS)

One of the records currently being challenged in Denver is the warmest September in climate history. So far this month the first 16 days have produced an average temperature of 72.6°F which is 3.2°F warmer than the previous record in 2015. With no significant cool downs in the extended outlook we have a strong chance to rewrite history.

Denver’s 30-year average temperature during the month of September is 63.4°F according to data from the National Weather Service. The top 10 warmest Septembers in the Denver climate record are listed below.

69.4°F – 2015
68.3°F – 1948
68.2°F – 1981
68.2°F – 1931
68.0°F – 1998
67.8°F – 2018
67.7°F – 1933
67.6°F – 1947
67.2°F – 2005
67.2°F – 1994

And it’s not just September 2019 that has been exceptionally warm. The average September temperature for the entire 2010s decade is far outpacing the previous record set during the 1930s. Below is a list of September’s average temperature by decade in Denver.

1870s – 61.9°F*
1880s – 62.2°F
1890s – 63.8°F
1900s – 62.6°F
1910s – 62.0°F
1920s – 62.2°F
1930s – 65.0°F
1940s – 64.1°F
1950s – 63.6°F**
1960s – 62.0°F
1970s – 61.8°F
1980s – 62.8°F
1990s – 63.7°F***
2000s – 63.3°F
2010s – 66.3°F****

Another very powerful statistic that shows just how warm it has been this decade comes from looking at the daily record highs in Denver. Of the 30 calendar days during September, 15 have daily record highs that have been set since the year 2010.

*Denver’s temperature record began in 1872, so the 1870s decade includes only 8 years of data

**Denver’s weather station moved from Lower Downtown to Stapleton in 1950

***Denver’s weather station moved from Stapleton to Denver International Airport in 1995, so the 1990s number was calculated using Stapleton data for 1990-94 and DIA from 1995-99

****The 2010s does not include data from 2019 since the month hasn’t ended

Chris Spears

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