Time series of monthly minimum and maximum temperature, precipitation and potential evapotranspiration were derived for 1337 watersheds in the conterminous United States for sites found in the national streamflow database, termed the hydroclimatologic data network (HCDN), developed by Slack et al. (1993a,b). Estimates were derived for the years 1951-1990.This HCDN data set consists of records of ... average daily streamflow at 1553 sites located throughout the United States. The data meet certain measurement accuracy criterion outlined by Slack et al. (1993). The HCDN contains river flows from 1874 to 1988, with an average record length of 44 years. The streamflow data included in the HCDN is purported to be relatively free from anthropogenic influences and the accuracy ratings of these records are at least rated good per USGS standards. A subset of the HCDN streamflow sites from 1337 watersheds with at least 10 years of record length was used. This subset includes 1376 HCDN sites.The climate characteristic estimates of temperature and precipitation were estimated using the PRISM (Daly et al. 1994, 1997) climate analysis system as described in Vogel, et al. 1999.Estimates of monthly potential evaporation were obtained using a method introduced by Hargreaves and Samani (1982) which is based on monthly time series of average minimum and maximum temperature data along with extraterrestrial solar radiation. Extraterrestrial solar radiation was estimated for each HCDN basin by computing the solar radiation over 0.1 degree grids using the method introduced by Duffie and Beckman (1980) and then summing those estimates for each river basin. This process is described in Sankarasubramanian, Vogel, and Limbrunner, 2001.The data files are organized in directories by parameter, Tmax, Tmin, Pre, and PET, and contain 18 subdirectories representing the 18 HCDN regions. Each region subdirectory contains data files for the monthly time series of respective hydroclimate attributes (Tmax, Tmin, Precipitation, and PET) for the individual HCDN sites in that region for the years 1951-1990. All files are in space delimited ASCII format.