This element was computed using snowfall data from the National Climatic Data Center's United States Snow Climatology (TD-9641M) database (NCDC, 1999c). The original snowfall data is given to a tenth of an inch. This element is given as a date range. The median and extreme dates of the first and last snowfall are presented within approximately biweekly ranges within the snowfall season (August - July). The median date is the 29-year median of the first or last date of measurable snowfall (at least 0.1 inch). Similarly, the extreme date is the absolute first or last date of measurable snowfall within the 29-year period. If no snow was observed for at least one-half of the years with available data, then the station was designated "RARE SNOW." If no snow was observed for any of the years with available data, then the station was designated "NO SNOW." The 29-year median and extreme dates were computed using snow season periods from August 1 - July 31. The first snow season commenced on August 1, 1961 and the last snow season ended on July 31, 1990. Daily snowfall measurements were based on the 24-hour period ending at the time of observation for a given station. In computing the monthly means, daily trace values of snowfall were treated as a value of zero. Data extracted for Arizona and 25 mile buffer.
