The State receives both South-west and North-east monsoons. The mean annual rainfall is 2693 mm. The highest rainfall is recorded (5883 mm) at Neriamangalam and the lowest (651 mm) at Chinnar in Idukki district. The Southern parts of Kerala experience both South-west and North-east monsoon while the northern districts of Kannur and Kasaragod receive very little rains from the north-east monsoons. Most part of the State is facing the Arabian sea, hence the South-west monsoon is active and accounts for 60 per cent of the annual rainfall on an average. The number of rainy days varies from 45-172 days in a year.

The mean annual temperature varies from 25.40C to 310C in the central parts of Kerala, while the temperature drops to 150C in the hills. March, April and May are summer months and the temperature rises to 400C in central plains. The mean relative humidity varies between 85-95 per cent during June and lowers to 70 per cent in summer.