Longest Stretch of High Heat Days

Longest Stretch of High Heat Days

This tool is excerpted from Chesapeake Bay Watershed Climate Impacts Summary and Outlook for Summer 2022.

Tool Background

Recent heatwaves in the Mid-Atlantic have brought temperatures over 95 degrees F to much of the region.1 Air conditioning use, however, which is one heat-related precaution that can be taken, is widespread in the Mid-Atlantic. Around 90 percent of homes in the region have air conditioning.2 At the same time, extreme heat is anticipated to increase into the future. This suggests a high potential for risk to human health, as well as related risks to infrastructure and resource management and economic activity.3,4,5

An examination of the length of consecutive high heat days and how they are expected to change into the future can help public health agencies, as well as other impacted groups, better plan for and adapt to extreme heat events. The following tool displays the longest annual stretch of high heat days over a historical period and into the future. Users can select a high heat temperature threshold most relevant to their interests, as well as future time periods, locations, and emissions scenarios.

Key Findings

  • The Mid-Atlantic region is projected to experience significant increases in the number of consecutive days above 90 degrees F. For some locations, stretches of high heat days could be 5–12 times longer than in the past.
  • By 2050, portions of southeastern Virginia could see over 5 consecutive days of temperatures above 100 degrees F and over 50 consecutive days of temperatures above 90 degrees F per year in a high emissions future.
  • By the end of the century, the Mid-Atlantic region could see up to 13 consecutive days of temperatures above 90 degrees F per year in a low emissions future, and 26 consecutive days in a high emissions future, compared to a historical average of three days.

Figure 1. Longest Annual Stretch of High Heat Days

How to Use the Tool

Selecting Temperature Thresholds, Time Periods and Future Emissions
Use the filters to the right of the maps to adjust the temperature threshold used to calculate the longest stretch of high heat days and the 30-year time period. Users can also select the future emissions scenario (Low or High Emissions).

Viewing Data for a State or County
Use the State and County filters to the right of the table to have the plot show data for a particular 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 sets6 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;7 and a high-emissions future, RCP 8.5.8 For this study, we used LOCA data over the Chesapeake Bay watershed from 1950–2100 (or 2099 for some models) for calculations of the baseline periods and the percent differences from those baselines. Access LOCA datasets and learn more about the methodology.