Historical Climatology Series (HCS) 4 and 5 is a series of digital products that the National Climatic Data Center (NCDC) offers to customers. The series is archived as the single digital data set DSI-9641E. HCS 4 and 5 is actually a subseries in a larger series of products called US Climate Normals. HCS 4-1 is state, regional and national monthly and annual temperatures, weighted by area, for the ... normals period 1971-2000, plus earlier thirty-year normals periods starting in 1931. HCS 4-2 is similar to HCS 4-1, except it is for precipitation. HCS 4-3 is similar to HCS 4-1 and 4-2, except it is state, regional and national seasonal temperatures and precipitation. HCS 5-1 is state, regional, and national heating degree days, weighted by population. HCS 5-2 is similar to HCS 5-1, except it is for cooling degree days.