This study analysed the daily incidence of sexual assault in Greater Manchester with respect to the local weather conditions throughout the year 2002. Cases seen at the St. Mary's Sexual Assault Referral Centre (including police and self-referred clients) for which the date of the assault was known were included in the study. The daily maximum, minimum, and mean temperature, rainfall, wind speed, and hours of sunshine recorded at Manchester Airport were used in correlation and regression analyses. Maximum temperature and hours of sunshine both had a statistically significant (p<0.05 and 0.01, respectively) positive relationship with the number of sexual assaults committed in a day.