This study examined the effects of weather on personality self-ratings. Single-assessment data were derived from the German General Social Survey conducted in 2008. For a subset of the participants (N = 478), official weather station data for the day a personality inventory was completed could be determined. Among these respondents, 140 (29%) completed the personality inventory on an unambiguously sunny day, 59 (12%) completed the measure on an unambiguously rainy day, and 279 (59%) completed the questionnaire on a day characterized by mixed weather conditions. Results revealed that self-ratings for some personality domains differed depending on the weather conditions on the day the inventory was completed. When compared with corresponding self-ratings collected under mixed weather conditions, ratings for the Big Five dimension of Openness to Experience were significantly lower on rainy days and ratings for Conscientiousness were significantly lower on sunny days. These results are suggestive of some limitations on the assumed situational independence of trait ratings.