September 2024 – Very Dry with Near Normal Temperatures

September Temperatures

Preliminary data indicates that the statewide average temperature in September was 69.3^°F, which is 0.2^°F above the 1991-2020 mean value of 69.1^°F (Figure 1).  September’s temperature was in the top one-third of months since records began in 1895.  

September Precipitation

Delaware’s statewide precipitation for September 2024 averaged 0.73 inches, 3.49 inches below the 1991-2020 mean of 4.22 inches (Figure 2).  September 2024 was the 3rd driest September since observations began in 1895. 

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures (Figure 3) varied between small positive and negative values depending upon the exact location across the State. Precipitation anomalies were uniformly negative across the entire state, with most departures ranging between 3 and 4 inches below normal for the month.  (Figure 4).

National Anomalies

Temperatures were above normal across nearly the entire United States in September (Figure 5). Some locations in the north-central portion of the country saw anomalies of up to 9^°F. Precipitation departures varied across the country (Figure 6).  Much of the eastern one-half of the United States saw above below normal precipitation except for the Southeast where tropical systems produced some areas of heavy precipitation during the month.  The Pacific Northwest was also dry during September.   The 500 hPa height pattern for September showed an anomalous jet stream ridge across much of the northern tier of the country (Figure 7) contributing to the temperature anomalies in these regions.

Global Anomalies

September 2024 ranked as the second warmest September on record for the globe since 1850.  Global temperatures were 1.24^°C (2.23^°F) above the 1901-2000 mean.  Particular warmth was found across western northern North America, Eastern Europe, and China (Figure 8).

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