The data set was computed using data from the National Climatic Data Center's U.S. National 1961-1990 Climate Normals (NOAA, 1994b). The original daily data and the element are in hundredths of an inch, with daily trace values designated as zero. The mean monthly values were computed by taking the 30-year mean of the monthly means. The monthly means were computed from the sum of the daily precipitation values for a given month. The mean annual value was computed by taking the 30-year mean of the yearly means. The yearly means were computed by averaging their 12 monthly mean values. Data extracted for Arizona and 25 mile buffer.