Changes in Extreme Precipitation from 1976 to Present

This tool is excerpted from Chesapeake Bay Watershed Climate Impacts Summary and Outlook for 2018.

Key Findings

  • The eastern half of the Chesapeake Bay Watershed has experienced increases in extreme precipitation from 2006-2017 compared to historical averages.
  • We see greater changes in the number of extreme precipitation events when looking at larger events.
  • Much of the eastern portion of the watershed has seen double the number of days with extreme precipitation over 3 inches. These are the largest daily events in our analysis.
  • Decreases in extreme precipitation events over the western portion of the watershed could suggest drying or at least decreases in the magnitude and intensity of precipitation events.

How to Use the Tool

Move the slider to adjust the Daily Precipitation Threshold to show number of days with precipitation above a 1", 2" or 3" threshold.

Click or tap a grid cell to show trends in the number of annual extreme precipitation events. This data will change when a different Daily Precipitation Threshold is selected.

Technical Notes

The ChesWx gridded climate datasets contain daily interpolations of precipitation and temperature observations for the Chesapeake Bay watershed, as well as the broader Mid-Atlantic and surrounding regions. Data are available from 1948 to 2017 at 4km spacial resolution. For this study, we utilized ChesWx daily precipitation data over the Chesapeake Bay watershed from 1976 to 2017. Access ChesWx data and learn more about the ChesWx methodology and input datasets.

We calculated the number of days above 1 inch, 2 inch and 3 inch daily precipitation thresholds ofr each year across the Chesapeake Bay watershed using the ChesWx precipitation data product. The annual counts above these thesholds were then averaged across two periods: 1976-2005 and 2006-2017. The ChesWx were masked to the boundaries of the Chesapeake Bay watershed, and the spacial resolution of each dataset was preserved.

  • Changes in Future Extreme Precipitation

    This tool is an interactive map of the Chesapeake Bay watershed that provides gridded estimates of how projections of future extreme precipitation—the number of days each year with precipitation above a 1", 2" or 3" threshold—during 30-year periods (2006-2035, 2036-2065, 2066-2095) and under two future emissions scenarios, compare to a historic 30-year average (1976-2005).

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