On August 1, 2011, the National Weather Service began using monthly climate normals that were derived from the past 30 years, from 1981 to 2010, inclusive.
For about 75 years, member nations of the World Meteorological Organization (WMO) have been computing monthly climate normals of temperature and precipitation. These normals are averages of 30 years of data. The first set of normals was computed for the 1901-1930 period. The WMO requires that the normals are updated every 30 years, resulting in normals also for 1931–1960 and 1961–1990. Since 1956, the WMO has recommended that each member nation recompute its normals every 10 years.
TED FATHAUER is an Atmospheric Science student at the University of Science in Fairbanks, Alaska.