PHOENIX, ARIZ. — September heat has reached some incredible extremes over the years across the United States, with NOAA data showing all-time September high temperature records ranging from a scorching 117 degrees in Phoenix down to a relatively mild 73 degrees in Anchorage.
Phoenix, Las Vegas and the Desert Southwest Hold the Hottest Records
Phoenix holds the hottest all-time September reading among major U.S. cities at 117 degrees, a record set on September 28, 2024. Las Vegas follows closely behind at 114 degrees, recorded on September 6, 2020, while Los Angeles checks in at 110 degrees from a September 26, 1963 heat wave. That trio of desert Southwest cities represents the upper end of what September heat can produce in the hottest corners of the country.
The presence of the Phoenix and Las Vegas records among the most recent entries on this list, both set within the last several years, stands out compared with several other cities whose records date back decades or even more than a century.
Texas Cities Cluster Around the Same Historic September Day
Several Texas and central Plains cities share the exact same record date, September 4, 2000, including Dallas at 111 degrees and Houston at 109 degrees. Oklahoma City set its own record just a day earlier, on September 3, 2000, at 108 degrees. That clustering of records around the same early September window suggests a significant, widespread heat wave gripped the south-central United States during that specific stretch of 2000.
Kansas City holds an even older record from this same general region, reaching 109 degrees on September 3, 1947, showing that intense September heat in this part of the country is not a purely modern phenomenon.
A Shared Heat Wave Struck the East Coast in 1881
Perhaps the most striking pattern in this data involves September 7, 1881, when Boston, Philadelphia and Washington, D.C., all set their all-time September high temperature records on the exact same day. Boston and Philadelphia both reached 102 degrees, while D.C. climbed to 104 degrees, reflecting what must have been an extraordinarily intense and widespread heat wave gripping the entire East Coast corridor that day…