Seasonal abundance patterns for Japanese encephalitis vectors along climatic variations were studied in the coastal areas of Alappuzha district from June 2012 to May 2013. A total of 10563 female mosquitoes belonging to eleven species were collected. Culex gelidusTheobald (50.04%), Cx. tritaeniorhynchus Giles (26.50%), and Cx. sitiens Wiedemann (7.55%) were found to be most common in these areas. Cx. sitiens females were collected from each sampling occasion from early monsoon season June to late summer May with a distinct peak in April at 7.18 electrical conductivity (EC). Cx. sitiens abundance increased rapidly when monthly salinity level consistently exceeded 7.76, occurring in March at 7.76 and April at 7.18 electrical conductivity (EC). While analyzing correlation of Cx. sitiens density with salinity and rainfall was significant. High density of Cx. gelidus was greatly influenced by total rainfall and it was found to be significantly correlated with Per Man Hour (PMH) (P < 0.05), whereas salinity was inversely correlated with mosquito density (P < 0.001). The abundance of Cx. tritaeniorhynchus was lowest in June (rainy season) and increased in October, with densities increasing sharply during summer season in April (83 PMH). During summer, due to increased salinity Cx. sitiens density increased. These areas may develop in to brackish and saline water populated by Cx. sitiens, which can be new vectors for Japanese encephalitis or West Nile virus in these areas.