Dengue and Leptospirosis are the two highest reported, vector-bourne, notifiable diseases of Sri Lanka. Each accountable for over 200 deaths in 2024 with a mortality rate of 1.2% and 1.7% respectively. Dengue virus is primarily transmitted to the human by the vector, Aedes aegypti mosquito which lays eggs in stagnant water whereas Leptospira virus transmitted through rodent urine and contaminated water. Climate plays a major role in the epidemiology of vector-bourne diseases and so it should be a concern in prevention, especially in a country like Sri Lanka with year-round rainfall. Objectives – Understand different geographical impediments in mitigating dengue and leptospirosis in Kalutara District Sri Lanka Methods – Retrospective Descriptive study of the incidence of Dengue and Leptospirosis in Kalutara District of Sri Lanka which was evaluated against the climate variation of the country over the year. Results – There’s a crude decline of notified number of dengue cases and rapid rise of Leptospirosis cases in the Kalutara district associated with the periods of higher rainfall (September to December). Same pattern was identified in the national context as well. Conclusion- Heavy rainfalls has contradictory effects on the epidemiology of dengue & leptospirosis. Heavy rainfalls wash away larvae of dengue vector mosquito which reduces the disease spread. They also causes heavy flooding which washes away leptospira vector rodents to reservoirs which increase the Leptospirosis transmission. Understanding this is important in planning the time frame for community based interventions to mitigate dengue and leptospirosis in Sri Lanka