Acute urinary retention (AUR) is characterized by a sudden and painful inability to pass urine and is the most common urological emergency. However, according to our knowledge, no study to date has attempted to explore the monthly variation of AUR after adjusting for climatic parameters. This study aimed to examine the monthly variation of AUR due to benign prostatic enlargement (BPE) in Taiwan. The data used in this study were sourced from 2 datasets: the Longitudinal Health Insurance Database 2005 and a meteorological dataset supplied by the Taiwan Central Weather Bureau. We identified 1406 patients aged 40 years or more with a diagnosis of BPE that could all be followed throughout a 6-year study period (2003-2008). We used the autoregressive integrated moving average (ARIMA) method to examine the incidence of AUR for seasonality. The results show that January (midwinter) had the highest rates, decreasing in March to a trough in June (early summer). The incidence then increased again and reached a peak in December (early winter). The ARIMA test also revealed significant monthly variation in the incidence of AUR. In addition, the ARIMA regression revealed that January, February, August, October, November, and December had significantly higher monthly incidence rates of AUR compared with June, after adjusting for the time trend effect and climatic parameters. Our study concluded that significant monthly variation in the incidence of AUR occurred, and January (midwinter) had the highest rates.