Purpose: To find the correlation between ambient temperature change and the efficacy of acupuncture on the postmenopausal hot flash. Methods: 52 patients entered a randomized clinical trial which was to verify the efficacy of acupuncture on postmenopausal hot flash. Participants were treated with optimal/minimal acupuncture in the course of 13 weeks. 34 of 52 visited for the temperature-rising period(Group 1), while 18 of 52 for the temperature-falling period(Group 2), 100mm hot flash VAS and average temperature were taken 18 times from each person. Linear mixed effects model was used to find the correlation between temperature and hot flash VAS score(p-value<0.05). Group1/2, optimal/minimal acupuncture, age, age of menarche, height, weight, percent body fat, BMI, waist-hip ratio, past history of hysterectomy and HRT were also examined. Results: Period of treatment had influence on the hot flash VAS. As time went by, hot flash decreased(p<.0000). Participants who underwent minimal acupuncture showed higher hot flash VAS(p=0.0479) and as waist-hip ratio rose, hot flash increased(p<.0000). As the temperature rose, hot flash VAS score became lower(p=0.0143) and it was because 34 of 52 participants were treated for the temperature-rising period. Group 1/2 had no interrelation with hot flash(p=0.5741). Conclusion: Hot flash diminished as participants were treated with acupuncture, independently of whether the ambient temperature rises or falls.