Future Projected 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

  • Similar to the trends in daily lows over the last several decades, the region is projected to see increases in the number of days with warm low temperatures.
  • The largest increases in the average annual number of days with warm daily low temperatures are projected for a daily low temperature threshold of 70°F. On average, the region as a whole could see 53 days above this threshold by late-century in a high-emissions future. The region currently experiences eight days above this threshold.
  • Under both future emissions scenarios, the southeastern portion of the Mid-Atlantic region is projected to experience the greatest increases in the number of days with warm daily lows.
  • In a high-emissions future, parts of western Pennsylvania could see more than 40 days per year with warm daily lows.
  • Future projections indicate that only a few regions might experience significant changes in the number of days with lows above 80°F. Included in this group are Baltimore, Maryland, and Washington, D.C.

How to Use the Tool

Selecting Time Periods and Future-Emissions Scenarios
Use the slider to the right of the maps to adjust the 30-year period used to calculate the average annual number of days with temperatures above the selected temperature threshold. Users can also select the future-emissions scenario (Low or High Emissions).

Viewing Variability Within a Location
Hover or tap over a point of interest. A window will pop up that displays the average annual number of days with low temperatures above the selected threshold. 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

Localized Constructed Analogs (LOCA) is a downscaled climate data product available at 1/16-degree (6-km) resolution over the continental United States. LOCA data sets1 include the 32 climate models available in the Coupled Model Intercomparison Project 5 (CMIP5) archive, for two future greenhouse gas concentration trajectories: a low-emissions future, Representative Concentration Pathway (RCP) 4.5;2 and a high-emissions future, RCP 8.5.3 For this study, we used LOCA data over the Chesapeake Bay watershed from 1981–2100 (or 2099 for some models). Access LOCA datasets and learn more about the methodology.

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. We averaged values across 30-year periods: 1981–2010, 2011–2040, 2041–2070, and 2071–2099 for LOCA data for a low-emissions future (RCP 4.5)4 and a high-emissions future (RCP 8.5).5 A weighted average was provided by the Northeast Regional Climate Center to average across climate models for each grid cell in the LOCA data set.6 The LOCA data sets were masked to the boundaries of the Mid-Atlantic region.