An analysis of weather conditions prior to and during the severe sweet potato whitefly (SPWF) outbreaks of 1981 and 1992 in Arizona revealed some striking similarities. Both bad outbreaks were preceded by 1) weak monsoons during the summer preceding the outbreak (1980 and 1991); 2) winters with very warm minimum temperatures and no incidence of extreme cold; and 3) springs with above normal temperatures and precipitation. The analysis also revealed the presence of above normal minimum temperatures during most winters since SPWF became an important pest in the Desert Southwest.