A group of 62 mostly university student subjects kept structured diaries of their feelings and their productivity for six weeks in Illinois in early autumn. During the same period, daily frequency of telephone calls to a crisis intervention service in the same community was monitored, and complete daily weather data for the vicinity were provided by a local meteorological research facility. Major findings are as follows. The weather appears to influence mood and productivity, but only to a smallextent compared with the aggregate of all other controlling factors. Males show a relatively stronger effect than females. Psychologically troubled people generally appear to be more affected by weather than university students. The students and the crisis intervention service clients with “mild” problems tend to be stressed more when the weather is unstable, cloudy, warm and humid, and least stressed during sunny, dry, cool weather with rising barometric pressure. The crisis service clients with “severe” problems react oppositely to these two weather types. The meaning of these and other results and the strengths and weaknesses of this study's design are discussed.