Historical Change in Date of Last Freeze and First Warm Day
This tool is an interactive map that provides county-level estimates of historic (1981–2019) annual dates of last frost, as well as dates of first 70°F and first 80°F maximum temperatures.
This tool is excerpted from Chesapeake Bay Watershed Climate Impacts Summary and Outlook for Spring 2020.
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 month displayed for each metric. Users can also select the future-emissions scenario (Low or High Emissions).
Viewing variability within a county:
Hover over or tap on a county of interest. A window will pop up that displays the percentage of dates for a given metric per month in each decade.
Localized Constructed Analogs (LOCA) is a downscaled climate data product available at 1/16th-degree (6-km) resolution over the continental United States. LOCA datasets1 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 dates of last frost, first 70°F maximum temperature and first 80°F maximum temperature. 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 datasets were masked to the boundaries of the Mid-Atlantic region.
More information on RCP 4.5 can be found in Allison M. Thomson, Katherine V. Calvin, Steven J. Smith, G. Page Kyle, April Volke, Pralit Patel, Sabrina Delgado-Arias, Ben Bond-Lamberty, Marshall A. Wise, Leon E. Clarke, and James A. Edmonds, “RCP4.5: A Pathway for Stabilization of Radiative Forcing by 2100,” Climatic Change, Vol. 109, 2011, pp. 77–94. As of June 8, 2020: https://doi.org/10.1007/s10584-011-0151-4Return to text ⤴
More information on RCP 8.5 can be found in Keywan Riahi, Shilpa Rao, Volker Krey, Cheolhung Cho, Vadim Chirkov, Guenther Fischer, Georg Kindermann, Nebojsa Nakicenovic, and Peter Rafaj, “RCP 8.5—A Scenario of Comparatively High Greenhouse Gas Emissions,” Climatic Change, Vol. 109, 2011, pp. 33–57. As of June 8, 2020: https://doi.org/10.1007/s10584-011-0149-y Return to text ⤴
More information on RCP 4.5 can be found in Thomson et al., 2011. Return to text ⤴
More information on RCP 8.5 can be found in: Riahi et al., 2011. Return to text ⤴