Preliminary data indicates that the statewide average temperature in December was 36.7°F, which is 1.4°F below the 1981-2010 mean value of 38.1°F (Figure 1). This was Delaware’s coolest December since 2010.
Delaware’s statewide precipitation for December 2017 averaged 1.08 inches, 2.49 inches below the 1981-2010 mean (Figure 2), making it the 5th driest December since 1895, and the driest in Delaware since 1988. Although the total liquid precipitation was much below normal for the State, the Wilmington – New Castle County Airport recorded 7.8 inches of snowfall during the month, more than twice the normal for December.
Statewide Spatial Averages
Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly below normal across the entire State (Figure 3), with some departures as large as 4o F below the 1981-2010 mean. Precipitation departures were below normal at each station (Figure 4), with most stations seeing departures of 2 – 3 inches below normal.