December 2024 – Cool and Dry Across Delaware

December Temperatures

Preliminary data indicates that the statewide average temperature in December was 38.7 ^°F, which is -0.8^°F below the 1991-2020 mean value of 39.5^°F (Figure 1).  December was one of only three months this year that saw below normal temperatures for the State.  

December Precipitation

Delaware’s statewide precipitation for December 2024 averaged 2.45 inches, 1.40 inches below the 1991-2020 mean of 3.85 inches (Figure 2).  December marked the 5^th month in a row with below normal precipitation values across Delaware.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures varied across the State, with generally small positive or negative anomalies depending on the specific location (Figure 3). Precipitation anomalies were negative across the entire state, with southeast Sussex County seeing the largest negative departures for the month (Figure 4).

National Anomalies

Temperatures were above normal across the entire United States in December (Figure 5), with locations in the Rocky Mountains and the High Plains seeing departures between 7^° and 9^° F.  Precipitation varied greatly across the country (Figure 6).   Much of the southern tier of the U.S. and the south Atlantic Coast saw below normal precipitation amounts, while the Pacific Northwest, portions of the Mississippi Valley and New England had greater than normal precipitation.  The 500 hPa height pattern for December showed an anomalous jet stream ridge across the western two-thirds of the United States (Figure 7) contributing to the temperature anomalies across the country.

Global Anomalies

December 2024 ranked as the second warmest December on record for the globe since 1850.  Global temperatures were 2.27^°F above the 1901-2000 mean.  Particular warmth was found across western North America and central Asia (Figure 8).

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