A Trend Toward Wetter Conditions

Madison is in the midst of its wettest 30-year period since weather records began in 1869. There has been an increase in precipitation since the early 1960s, culminating in the record 32.8" annual average during the period from 1971-2000. This record value will increase further from any more precipitation Madison receives this year. By comparison, the current "normal" mean annual precipitation for Madison--defined as the average from 1961-1990--is 30.9", and the previous 30-year record from 1876-1905 was 32.5".

Undoubtedly, shifts in the location of precipitation measurements within Madison have some bearing on the recorded amounts. For example, official readings were taken at the Dane County Regional Airport from 1951-2000, whereas they were made on the University of Wisconsin campus from 1905-1950. However, during their overlapping period from 1948-1963, the two stations' mean annual precipitation amounts agree to within 2%. In addition, Madison's trend toward wetter conditions is part of a much larger-scale pattern of precipitation increases in recent decades. Since the middle of the twentieth century, precipitation values have risen significantly across the U.S. and at most stations in the Northern Hemisphere (Karl et al., 1993; Groisman and Easterling, 1994).