The CEI was first presented in 1995 as a framework for quantifying observed changes in climate within the contiguous United States. The index is based on an aggregate set of conventional climate extreme indicators which now includes extremes in land- falling tropical storm and hurricane wind intensity. Originally, the CEI was calculated on an annual basis, and now the revised CEI is evaluated for eight standard seasons: spring, summer, autumn, winter, annual, cold season, warm season, and hurricane season. NOAA has also developed a regional CEI, providing data for 9 regions of the contiguous US.
National Center for Atmospheric Research Staff (Eds). Last modified 31 Oct 2013. "The Climate Data Guide: U.S. Climate Extremes Index (CEI)." Retrieved from https://climatedataguide.ucar.edu/climate-data/us-climate-extremes-index-cei.