This element was computed using data from the National Climatic Data Center's Cooperative Summary of the Day (TD-3200) database (NCDC, 1995). The original data and this element are given in hundredths of an inch. This element is given as number of whole days. The monthly values were computed by taking the 30-year mean of the number of days with measurable precipitation (at least 0.01 inch) 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 number of days with measurable precipitation. Data was extracted for Arizona and 25 mile buffer.