Preliminary data indicates that the statewide average temperature in January was 37.1° F, which is 3.0° F above the 1981-2010 mean value of 34.1° F (Figure 1). January 2021 was the 28th warmest since observations began in 1895, placing it in the top one-third of all Januarys.
Delaware’s statewide precipitation for January 2021 averaged 2.33 inches, 0.99 inches below the 1981-2010 mean (Figure 2). This placed this month’s precipitation total as the 25th lowest of all Januarys since 1895, tied with January 1969. Snowfall totaled 2.5 inches for the month at the Wilmington/New Castle County Airport, and this fell on the last day of the month. Normal snowfall for January is 5.9 inches.
Statewide Spatial Anomalies
Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were positive at all stations, with the largest anomalies found across New Castle County (Figure 3). Precipitation was generally below normal throughout the State.
Temperatures were above normal across the majority of the United States, with the largest temperature anomalies (10° F – 13° F) found across the north-central portion of the country (Figure 4). Only the southwest United States saw below normal January temperatures. Precipitation anomalies varied greatly across the country with particularly heavy precipitation across the central United States, while the northern tier of the country and Florida saw very dry conditions (Figure 5). The 500 hPa height pattern for January shows a very strong jet stream ridge across northeastern North America resulting in the warm conditions across the northern portions of the country (Figure 6).