The Jaffna Peninsula has the same climate as that of the dry zone of Sri Lanka. Since the Peninsula lies within ten degrees of latitude north of the equator there is "high incidence of solar rays at all times of the year". However, the "processes of convection, adiabatic cooling and resulting condensation" leading to humidity and land-sea breezes make the temperature conditions more equable on the sea board.
The average temperature in Jaffna is the highest in the Island. It is approximately 83 degrees E (28.33 C.) Dryness causes extreme temperatures during the southwest monsoon and the heat wave of India affects the area during the months of April and May.
In the months of April - May and August - September, when the sun is overhead, the temperature stands at maximum. The coolest period occurs in December - January coinciding with the lowest sun.
The annual rainfall varies from one place to the other and also from year to year. The western part of the Peninsula enjoys the mean annual rainfall of less then 50 inches whereas the eastern part has between 50 to 75 inches. The total average rainfall for 1932 was 73.79 inches and for 1936 was 32.44 inches. It is also calculated that rainfall during the northeast monsoon forms 82% of the total annual fall.
Rainfall does not affect the temperature to any great extent for two reasons: because of humidity and because the Peninsula has no mountains. It has no streams either "unless those percolationís can be so called which make their way underground and rise thro' the sands on the margin of the sea at low water".