Daily rainfall records for 50 years (1961 to 2010) were used to determine the start and end of rainy seasons in the southwestern region of Sri Lanka. The study was based on data records obtained from two weather stations in Colombo and Galle situated in the western and southern coastal belts of Sri Lanka, respectively, that have two growing seasons, Yala and Maha. The start and end dates were determined by using a method that is based on cumulative rainfall measured during a season. Substantial interannual variability is seen in start and end of rainy seasons in this study. For the Yala season, the mean start and end dates are in the standard weeks 12.0 ± 2.3 and 24.1 ± 2.0 (March 24 to June 20), respectively. For the Maha season, the mean start and end dates are in the standard weeks 35.4 ± 2.0 and 49.6 ± 2.0 (September 5 to December 15), respectively. The mean durations of the rainy season for Yala and Maha are 12.1 ± 2.6 weeks and 14.2 ± 2.3 weeks respectively. The start date and the duration of the rainy season for both Yala and Maha are correlated, leading to early start dates resulting in longer rainy seasons. It can be concluded from this study that it is possible to use daily rainfall records to determine the mean start and end dates of rainy seasons in the southwestern region of Sri Lanka.

50 年（1961 年至 2010 年）的日降雨量记录被用来确定斯里兰卡西南部地区雨季的开始和结束。该研究基于从分别位于斯里兰卡西部和南部沿海地带的科伦坡和加勒的两个气象站获得的数据记录，这些气象站有两个生长季节，即雅拉和玛哈。开始和结束日期是通过使用基于一个季节测量的累积降雨量的方法确定的。在这项研究中，在雨季的开始和结束时可以看到显着的年际变化。对于也拉季节，平均开始和结束日期分别在标准周 12.0 ± 2.3 和 24.1 ± 2.0（3 月 24 日至 6 月 20 日）内。对于 Maha 季节，平均开始和结束日期在标准周 35.4 ± 2.0 和 49.6 ± 2.0（9 月 5 日至 12 月 15 日），分别。雅拉和玛哈雨季的平均持续时间分别为 12.1±2.6 周和 14.2±2.3 周。Yala 和 Maha 的开始日期和雨季持续时间是相关的，导致提前开始日期导致更长的雨季。本研究可以得出结论，利用日降雨量记录来确定斯里兰卡西南部地区雨季的平均开始和结束日期是可能的。