May 2015 Warm and Dry Across Delaware

Figure 1. Delaware statewide mean May temperature (°F) 1895-2015.

Figure 2. Delaware statewide May precipitation (inches) 1895-2015.

May Temperatures

Preliminary data indicates that the statewide average temperature in
May was 67.97°F; this was 5.2°F above the 1981-2010 normal of 62.7°F (Figure 1), making May 2015 the third warmest on record since 1895. This is the seventh year in a row that May temperatures have
been above normal.

May Precipitation

Delaware’s statewide precipitation for May 2015 averaged only 1.47 inches, 2.39 inches below the 1981-2010 mean (Figure 2). May 2015 was the tenth driest May since records began in 1895.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows that May temperatures were above normal across nearly all of

Delaware and Chester County, PA, with several stations seeing anomalies of greater than 6o F (Figure 3). Precipitation was below normal at all locations across the State with negative departures of over three inches at several DEOS stations
(Figure 4).

Figure 3.May 2015 average temperature departures (°F) from the 1981-2010 mean based upon DEOS station data.

Figure 4. May 2015 precipitation departures (inches) from the 1981-2010 mean based upon DEOS station data