An annual rhythm in the battering of women.

Over 27,000 reports about women abused by their live-in male partners were provided by 23 shelter organizations in five locations in the United States. Cosinor analyses revealed statistically significant annual rhythms in the frequencies of abuse, with maxima in the summer. The rhythms were closely related to annual changes in ambient temperature in these locations, and the time of the maxima was similar to those previously reported for assaults and rapes. The findings support the hypothesis that violence by men toward women increases in summer independently of any major seasonal changes in the opportunity for contact between perpetrator and victim.