Changes in Extreme Precipitation in the Northeast United States: 1979–2014

Extreme precipitation can have significant impacts on infrastructure and property, human health, and local economies. This study examines recent changes in extreme precipitation in the Northeast United States, which here includes the states of Maine, New Hampshire, Vermont, New York, Massachusetts, Connecticut, Rhode Island, Pennsylvania, and New Jersey. From the United States Historical Climatology Network, daily station data at 58 stations missing less than 5% of days for the years 1979–2014 was used to analyze both total and extreme precipitation, with the latter defined as the top 1% of days with precipitation.

Results indicated both seasonal and spatial variability in extreme precipitation in the Northeast. The threshold for the top 1% of precipitation increased from 41.4 mm in the winter, to 58.9 mm in the fall season. The coastal areas had more intense extreme events (55–75 mm) that occurred less frequently (36–54 events between 1979–2014) than that of inland stations, which had less intense (38–55mm) but more frequent extreme precipitation events (55–75 events between 1979–2014). A statistically significant increasing trend of average and extreme precipitation was found in both precipitation amount (0.28 mm decade^-1 and 2.78 mm decade^-1, respectively) and frequency (6.94 average events decade^-1 and 4.44 extreme events decade^-1, respectively), especially during the summer and fall seasons. Further investigation into the causes of the observed increase in the frequency and intensity of extreme events, particularly into changes in the types of weather that lead to these events, will be completed.