Climate Projections 2050 (Annual Extreme Heat Days)

This feature layer, also referred to as an overlay on the Environmental Health Disparities (EHD) Map, shows four climate projections for Washington state. This layer is made of four different projections: 1. Change in Annual Precipitation, 2. Annual Extreme Heat Days, 3. Annual Change in Cooling and 4. Annual Change in Heating Degree Days. These project heat and precipitation data to the period around 2050 (2036-2065). This feature layer was created to support the EHD Map and the Washington Tracking Network (WTN). These projections do not factor into the EHD ranking or the designation of highly impacted communities. It is available for planning local implications of climate change. These climate projections only project heat and precipitation. They do not include important factors such as inland and coastal flooding, or wildfire risk. Annual Change in Precipitation: This projection shows the change in precipitation from the historical baseline. Climate change impacts mean heavier rainfall, and more precipitation falling as rain instead of snow. As a result, areas of Washington will see more flooding, flash floods, and landslides. Adaptations to prepare for these events might include additional planning for flooding, landslides, and drought Annual Extreme Heat Days: These data show the relative increase in hot days that will affect an area compared to the historical (1976-2005) threshold. This is different from cooling and heating degree days, which are absolute measures of the increase in temperature. This projection captures the percentage increase in extreme heat days from the historical threshold. Areas that have historically experienced fewer extreme heat days may feel greater impacts from extra extreme heat days than areas that historically experience them. Climate adaptations might include increased air conditioning installation in areas that previously haven’t needed them. Change in Cooling Degree Days and Heating Degree Days: Cooling and heating degree days measure how much the weather varies from 65 degrees Fahrenheit. This indicates how much energy is needed to heat or cool buildings. Both an increase (positive number) in cooling degree days and a decrease (negative number) in heating degree days indicate warming temperatures. Adaptations to deal with warmer climates can include such things as cooling centers and increased urban tree canopies. Citation Washington Tracking Network, Washington State Department of Health. Web. "Climate Projections 2050 (Extreme Heat Days)". Data for this layer was obtained from Phase 5 of the Coupled Model Inter-comparison Project (CMIP5). Published June 2026.