Statewide mean annual temperature in 2016 was 57.2°F according to preliminary data from the National Center for Environmental Information (NCEI). This was 1.8°F above the 1981-2010 normal of 55.4°F (Figure 1) and was tied with two other years as the 5th warmest year in Delaware since 1895. Monthly temperatures varied greatly throughout the year (Figure 2). The first three months of 2016 saw above normal temperatures, including the 4th warmest March since 1895. The only two months of the year with below normal temperatures followed in April and May. The last seven months of the year saw above normal temperatures, with some extreme warmth during this period including the 5th warmest July, the warmest August, and the 6th warmest September since records began in 1895. In addition, the summer season (JJA) 2016 was the 4th warmest since 1895.
Statewide precipitation in 2016 averaged 46.76 inches, 2.43 inches above the 1981-2010 mean of 44.33 inches (Figure 3).
Monthly precipitation anomalies varied between positive and negative throughout the year, with eight months of below normal and four months of above normal precipitation (Figure 4). September saw the largest precipitation anomaly of 5.45 inches above the 30-year normal, helping to push the annual value above the long-term mean.
Statewide Spatial Averages
According to data from the Delaware Environmental Observing System (DEOS; deos.udel.edu), mean annual temperature anomalies varied across Delaware (Figure 5). Northern New Castle County and Chester County, PA along with central Sussex and southern Kent counties had the largest positive temperature departures for the year.
Precipitation across the region varied dramatically in 2016 (Figure 6). Much of southern Delaware saw a 5 – 10 inch precipitation surplus during the year, while portions of northern New Castle County and Chester County, PA saw 5 – 10 inch precipitation deficits.