Sky Harbor against normal, September 2026
September 2026 at Sky Harbor ran 1.4°F above normal. Normal here is the 1991-2020 average for that same month, which is the standard climate baseline — so this is a comparison with the recent past, not with the start of the record.
Across the whole series, September has averaged -2.0°F against that baseline, over 79 years. The warmest was +5.4 (2024) and the coldest -10.0 (1965). A single month is weather; the reason to post one every month is that the band they fall in has moved — which is what the 12-month average on the chart is there to show.
The station is the caveat. One weather station stands for the whole metro: Phoenix Sky Harbor International Airport (NOAA USW00023183), whose record goes back to 1933 (this chart starts in 1948). Since then the city has grown around it from about a hundred thousand people to millions, and pavement holds heat through the night, so some of the warming in this line is the city and not the climate. That is why the anomaly is measured against a fixed 1991-2020 baseline rather than against the early record.
Source: NOAA Global Historical Climatology Network daily records for Phoenix Sky Harbor International Airport (USW00023183), via RCC-ACIS, aggregated to monthly means and differenced against the 1991-2020 normal for each calendar month. Auto-generated each build.