Historical Average Annual Number of Days with Warm Low Temperatures

This tool is excerpted from Chesapeake Bay Watershed Climate Impacts Summary and Outlook for Summer 2020.

Key Findings

  • In each decade since 1981–1990, the region as a whole has seen an increase in the number of days with warm daily low temperatures.
  • The southern portion of the Mid-Atlantic region experiences a higher number of days with warm daily low temperatures each decade.
  • The far-northern portions of region and high elevation locations, such as parts of West Virginia and northwestern Virginia, tend to see either very few or zero average annual number of days with warm daily low temperatures.

How to Use the Tool

Selecting Time Periods and Temperature Thresholds
Use the Time Period slider bar to adjust the decade used to calculate the average annual number of days above the selected temperature threshold. The daily low temperature threshold can also be selected by using the slider titled Temperature Threshold.

Viewing Variability Within a Location
Hover or tap over a point of interest. A window will pop up that displays the number of days above the selected temperature threshold in each decade. You can also use the Filter by State and Select by County filters to the right of the map to zoom into a location of interest.

Technical Notes

These maps were generated with gridded temperature estimates from the PRISM Climate Group at Oregon State University. Parameter-Elevation Regressions on Independent Slopes Model (PRISM) daily minimum temperature data are available at a 4-km resolution for the coterminous United States. Data were processed by the Northeast Regional Climate Center to extract the annual number of days with daily low temperatures above 70°F, 75°F and 80°F. More information on PRISM data can be found at http://www.prism.oregonstate.edu.

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