Preliminary data indicates that the statewide average temperature in April was 55.7o F, which is 2.2o F above the 1981-2010 mean value of 53.5o F (Figure 1). April 2021 was the 13th warmest April since observations began in 1895.
Delaware’s statewide precipitation for April 2021 averaged 2.25 inches, 1.39 inches below the 1981-2010 mean (Figure 2). This placed this month’s precipitation total in the bottom one-third of all years since 1895.
Statewide Spatial Anomalies
Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were positive at most stations, with the largest positive anomalies found across New Castle County (Figure 3). Precipitation was below normal at nearly all stations throughout the State with the largest negative anomalies found across eastern Kent County (Figure 4).
Temperatures were generally below normal across the central portion of the United States, and warmer than normal along both the Pacific and north-Atlantic coasts (Figure 5). Precipitation anomalies varied greatly across the country with particularly dry conditions across most of the western half of the United States. The Gulf Coast, from Louisiana east to Florida, saw much above normal precipitation (Figure 6). The 500 hPa height pattern for April shows a jet stream ridge across the Pacific Coast and a weak jet stream trough across the central and eastern portions of the country (Figure 7), contributing to the overall temperature pattern.