Special Report

American Cities With the Most Unusually Warm Temperatures This Year

The United Nations Climate Change Conference, also known as COP26, ended Nov. 12 in Glasgow, Scotland, with significant differences among nations on how to keep global temperatures from rising more than 1.5 degrees Celsius (34.7 degrees Fahrenheit) above pre-industrial levels and how to compensate poorer nations for the climate havoc inflicted on them by rich nations.

While people argue over global warming — including many who still deny human activity has anything to do with it — and what to do about it, temperatures keep climbing. (This city emits the most carbon dioxide in the world.)

The global average temperature has risen by 0.14 degrees Fahrenheit per decade since 1880, but the rate of warming over the past 40 years has been more than double that, at 0.32 degrees, according to the U.S. National Oceanic and Atmospheric Administration. The 10 warmest years on record have occurred since 2005, and there’s no end in sight. (These are 25 cities where rising seas could leave millions homeless.)

Rising temperatures have a significant incremental impact on local weather and the environment. They significantly alter weather patterns, causing more severe and frequent storms, and increase the frequency of droughts. The knock-on effects include a greater range of infectious diseases that thrive in warmer climates.

In the U.S., the effects of rising temperatures are already causing intense flooding in urban and suburban areas of the Northeast, insect outbreaks and tree diseases in the Northwest, damages to energy and agricultural infrastructure in the Southeast, extreme heat and flooding across the Midwest, and seasonal wildfires across the West. 

To determine the 25 U.S. cities with the most unusually warm temperatures this year, 24/7 Tempo reviewed data on average temperatures in September from the National Centers for Environmental Information of the NOAA. Cities were ranked based on the highest difference in the average temperature in September 2021 from the historical average temperature for September from 1901 to 2000. Data on the hottest and coldest September months on record also came from the NCEI, with records dating back to 1895. Data for cities in Hawaii was not available.

This list of U.S. cities that had far hotter temperatures in September than their historical average are mostly inland and in the northern and central parts of the contiguous 48 states. Among the 25 cities, North Dakota has five, while Kansas and Nevada are home to three, including Las Vegas. The only cities on this list outside this region are Montpelier, Vermont, and Lubbock, Texas. 

Temperatures in the cities on the list were at least 5.2 degrees above their respective historical averages in September. In the hottest city, they were 7.8 degrees above historical average. 

Click here to see the U.S. cities with the most unusually warm temperatures this year