Is a Warming of 1.1 Degrees C Unusual?

April 11, 2026

Commentary by Dr.-Ing. Bernd Fleischmann on the blog post “The Warmth of March 2026 in the USA”

Symbol image, generated by Grok AI.

The cause of the high temperatures around March 20, 2026, was a heat dome, the likes of which occur in the Midwestern United States every few decades. Looking at the temperatures in Phoenix, Arizona, one finds:

• • The 105°F maximum temperature from March 19 to 21 is 5°F above previous maximums for this period, but only 1°F above the 104°F that occurred in early April 1989.

  • The highest temperature ever recorded in Phoenix was 122°F during the heat dome of late June 1990.

  • For some days, the record highs are over 100 years old (Jan 18; June 11 and 12; July 2, 3, 6, and 23; Aug 6; Sept 8 and 23). The highest May temperatures were recorded in 1910.

  • The warmest year in Phoenix was 1934, the first year of the Dust Bowl era. Some of the temperature records for several states that still stand today originate from this year and the following two.

  • The change in measurement methods—from the previously common Stevenson screens with sluggish thermometers to today’s electronic thermometers in smaller housings—makes a difference of up to 1°C for daily maximum temperatures on sunny days with little wind.

  • Finally, the Urban Heat Island (UHI) effect: The population of Phoenix has increased nearly a hundredfold from the 1930s to today. This leads to a temperature increase of up to 5°C in the city center on low-wind days.

Conclusion

A heat dome is a weather phenomenon that has led to record temperatures in the Western USA multiple times before. Record temperatures in many U.S. states still date back to the period between 1934 and 1936, even though the urban heat island effect has increased significantly since then and amounts to up to 5°C for Phoenix, Arizona, for example. Media reporting on the heat in March 2026 is alarmist because it fails to mention these facts.

Dr.-Ing. Bernd Fleischmann
Klimanachrichten