Preliminary data indicates that the statewide average temperature in October was 60.8o F, which is 3.7o F above the 1981-2010 mean value of 57.1o F (Figure 1). October 2020 was tied with 1990 as the 9th warmest October since observations began in 1895.
Delaware’s statewide precipitation for October 2020 averaged 5.16 inches, 1.70 inches above the 1981-2010 mean (Figure 2), placing this month’s precipitation total in the top one-third of all months since 1895.
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 Sussex County (Figure 3). Precipitation was above normal throughout the State, with departures of greater than four inches across much of southern Delaware (Figure 4).
Temperatures were above normal across the western and eastern portions of the United States (3 – 7o F), while below normal temperatures were found across the Great Plains, especially from Montana east through Minnesota (Figure 5). Precipitation was far below normal across the southwestern portions of the country, with above normal precipitation covering much of the eastern one-third of the United States (Figure 6). The 500 hPa height pattern for October exhibits a strong trough across the north-central portions of the country and ridging along both the Atlantic and Pacific coasts (Figure 7).