Preliminary data indicates that the statewide average temperature in December was 50.5°F; this was 12.4°F above the 1981-2010 normal of 38.1°F (Figure 1), making December 2015 the warmest on record since 1895. This December was 6.1°F above the second warmest December on record that occurred in 2001. To put this in perspective, December 2015 was nearly 3.0°F above the November long-term average temperature and 6.0°F above the long-term average March temperature for the First State.
Delaware’s statewide precipitation for December 2015 averaged 4.68 inches, 1.11 inches above the 1981-2010 mean (Figure 2). December 2015 saw no snowfall accumulations anywhere in the State.
Statewide Spatial Averages
Data from the Delaware Environmental Observing System (DEOS) shows the unprecedented warmth across all of Delaware and Chester County, PA (Figure 3). Several stations in northern New Castle County, DE and Chester County, PA saw anomalies between 13°F and 14°F above the 30-year normal for December.
Precipitation was above normal across the entire State, with the largest positive departures found across southern New Castle County (Figure 4).