Introduction: World over studies are being done by different group of workers to understand the time of deliveries conducted. Surprisingly majority of deliveries were following a pattern, seasonally. Today in this busy world, couples choose comparatively a free time for delivery and preparation for conception is done accordingly. Apart from these, it is clearly shown majority of deliveries are conducted during a particular season. We hypothesised that the change in semen quality during different seasons is responsible for this phenomenon. Materials and methods: Present study conducted on semen quality included 12,408 semen samples collected from different laboratories of Bangalore city during 8 years (2000-2007) period of time and were analysed season wise. Results: Results showed sperm concentration was significantly lower in monsoon than in winter season. Humidity and pressure influenced sperm count. Forward moving sperms were influenced by temperature and pressure. The study concludes the change in birth rates seen during different season in a year is due to the quality of semen responsible for conception.