BACKGROUND: Females who misuse alcohol experience high rates of negative physical and mental health consequences. Existing findings are inconsistent but suggest a relationship between ovarian hormones and alcohol use. We aim to clarify how alcohol use and drinking motives vary across the menstrual cycle in female psychiatric outpatients using the luteinizing hormone (LH)-confirmed cycle phase. METHODS: Daily self-reports (n = 3721) were collected from 94 naturally cycling females, recruited for past-month suicidal ideation, during the baseline phase of three parent clinical trials between February 2017 and May 2022. Multilevel logistic and linear models estimated the relationship between the cycle phase (with LH-surge confirmed ovulation) and daily alcohol use or drinking motives, moderated by the weekend. Models were adjusted for age, legal drinking status, substance use disorder, and the COVID-19 pandemic, and included random effects. RESULTS: Participants were generally more likely to drink in the midluteal (vs. perimenstrual) phase, but more likely to drink heavily on weekends in periovulatory and perimenstrual (vs. midluteal) phases. Social motives for drinking were significantly higher on weekends in the periovulatory, mid-follicular, and midluteal phases (vs. weekdays), but this finding was non-significant in the perimenstrual phase. Participants rated drinking to cope higher in the perimenstrual phase (vs. midluteal phase), regardless of the weekend. CONCLUSION: In a psychiatric sample with LH-surge-confirmed ovulation, we find an increased likelihood to drink heavily in periovulatory and perimenstrual phases on weekends. We also find that the perimenstrual phase is associated with increased drinking to cope, and relatively lower weekend social drinking. Finally, random effects across models suggest individual differences in the extent to which the cycle influences drinking. Our findings stress (1) predictable phases of increased high-risk alcohol use across the menstrual cycle, and (2) the importance of individual assessment of cyclical changes in alcohol use to predict and prevent ovulation- and menses-related surges in heavy drinking.