This document describes a database containing monthly temperature and precipitation data for 1221 stations in the contiguous United States. This network of stations, known as the United States Historical Climatology Network (US HCN), and the resulting database were compiled by the National Climatic Data Center, Asheville, North Carolina. These data represent the best available data from the United States for analyzing long-term climate trends on a regional scale. The data for most stations extend through December 31, 1994, and a majority of the station records are serially complete for at least 80 years. Unlike many data sets that have been used in past climate studies, these data have been adjusted to remove biases introduced by station moves, instrument changes, time-of-observation differences, and urbanization effects. These monthly data are available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP includes this document and 27 machine-readable data files consisting of supporting data files, a descriptive file, and computer access codes. This document describes how the stations in the US HCN were selected and how the data were processed, defines limitations and restrictions of the data, describes the format and contents of the magnetic media, and provides reprints of literature that discuss the editing and adjustment techniques used in the US HCN.

This document describes a data base containing daily observations of maximum and minimum temperature and precipitation amounts from 138 US stations. These stations are a specially chosen subset of the 1219-station US Historical Climatology Network (HCN), compiled by the National Climatic Data Center (Asheville, North Carolina). The daily data network (herein referred to as the HCN/D) consists of stations considered to be the best of those from the HCN, selected to provide reasonably homogeneous spatial coverage of the contiguous US after considering the temporal homogeneity of each station's observing times, instrument types/positions, and surroundings. The data for each station extend through 1987, and most station records are complete for at least 80 years. The daily resolution of these data lends maximum flexibility for studies attempting to detect and monitor long-term climatic changes on a regional scale. Studies using daily data may be able to detect changes in regional climate that would not be apparent from analysis of the more commonly used monthly temperature and precipitation data. Such studies may include analyses of trends in maximum/minimum temperatures, temperature extremes, daily temperature range, precipitation ''event size'' frequency, and the magnitude and duration of wet and dry periods. Other applications of the data include planning and risk assessment in areas such as agriculture, natural resource exploration, and construction. This document describes how the stations in the HCN/D were selected, defines limitations and restrictions of the data, describes the format and contents of the magnetic tape, and provides reprints of literature pertinent to the collection and application of daily climate data.