The climatic factors of temperature, humidity and rainfall are distinctly different between
the plains and hills. When the plains are uncomfortably hot and humid during the summer months,
the microclimate under influence of elevation and presence of evergreen vegetation renders the
weather of the upper reaches of the hills, cool and pleasant. Dr K Kandiannan, Dr C K Thankamani
and Dr P A Mathew of Indian Institute of Spices Research Calicut, Kerala, had done an “Analysis
of rainfall of the high rainfall tract of agro-climatic zone of Kerala”. The salient
findings are given below.
Kerala has been divided into five agro-climatic zones based on physiography, climate, soil
characteristics, sea water intrusion, irrigation facilities and land use pattern (KSLUP 1997).
The northern agro climatic zone consisting of Kasaragod, Kannur, Kozhikode and Malappuram
districts covering 28.2% of the area of the state, receives rainfall during both south-west
and north-east monsoons with an annual average rainfall of 3379 mm. The south-west monsoon
current, which brings in most of the annual rainfall, gets a forced ascent at the Western
Ghats and the windward slopes experience very heavy rainfall, which is not uniformly distributed.
These western windward slopes form the watershed for a large number of rivers (Simon and
Both south-west and north-east monsoons bring rains to this region. South West monsoon is
heavier and more violent. The 1992 and 2007 monsoon season was unusually heavy and violent
causing considerable damage to forest, cultivations and property. The south west monsoon
starts in the first week of June, preceded by a few pre monsoon showers in April and May.
The heaviest fall occurs in July and August. The north east monsoon is generally weak and
characterized by sporadic rains during afternoons in the month of October-November.
December to March is generally dry months.
The temperature varies from 16° C to 38° C, diurnal and seasonal variation being moderate,
as typical of the tropical nature. As the altitude increases, the variation is comparatively
minimal which is between 80c and 250c. The hottest months are April and May. December to
February is relatively cool.
At the hills, the humidity varies from 60% to 100%. In the plains and foot of the hills,
humidity varies from 50% to 90%, reaching saturation point during monsoon season. Mist is
frequent in the higher elevation, with heavy deposition during December - February.
Regular winds lash the area during the southwest monsoon period. Strong eddy winds that
fan along the foothills are also experienced during monsoon causing widespread damage to
properties and cultivations. The dry winds experienced during summer pose fire hazard in
the deciduous forests adjoining to the human habitations.
High rainfall obtained in Kakkayam and Peruvannamuzhy together with other geographical and
soil conditions bring in specialized microclimatic situations leading to a peculiar habitat,
which support relatively specialized vegetation. Such patches could be one reason for the
high level of endemism reported in Malabar wildlife sanctuary.