Preliminary data indicates that the statewide average temperature in September was 70.2°F, which was 2.2°F above the 1981-2010 normal of 68.0°F (Figure 1). September 2017 was the 19th warmest September since 1895.
Delaware’s statewide precipitation for September 2017 averaged 2.17 inches, 1.43 inches below the 1981-2010 mean (Figure 2), placing it in the driest one-third of Septembers since records began in 1895.
Statewide Spatial Averages
Data from the Delaware Environmental Observing System (DEOS) show that temperatures were above normal across the majority of the State with the largest positive temperature departures found across Chester County, PA and northern New Castle County, DE. (Figure 3). All stations in the DEOS network recorded below normal precipitation except for extreme southeastern Delaware (Figure 4). In the northern portions of the region, negative precipitation departures reached over 3 inches at several stations.