The winds over the State are seasonal only in the region of Palghat Gap where winds are predominantly from the east in the period from November to March and from west in the rest of the year. In other parts of the State flow of wind is mainly governed by differential heating of land and water mass together with mountain winds. Winds have westerly component during the day and easterly components during the night through the year. In general winds are quite strong during afternoons when the thermal circulation is best developed and weak during night.

As the State stretches from north to south with the Arabian Sea in its west, relative humidity is in general high over the State. In the period January to March afternoon humidity reduce to 60 - 63%, varying from 35% in the interior to 71 % in the coastal area. The diurnal variation in relative humidity during this period is maximum and ranges from 4 to 16%, depending upon the proximity of the sea. The relative humidity in the monsoon period rises to about 85% for the state. The variation in this period is minimum.

Day temperatures are more or less uniform over the plains throughout the year except during monsoon months when these temperatures drop down by about 3 to 5°C. Both day and night temperatures are lower over the plateau and at high level stations than over the plain. Day temperatures of coastal places are less than those of interior places. March is hottest month with a mean maximum temperature of about 33°C. Mean maximum temperature is minimum in the month of July when the State receives plenty of rainfall and the sky is heavily clouded. It is 28.5°C for the State as a whole in July, varying from

about 28°C in the north to about 29°C in the South. Inland stations experience higher maximum temperatures than the coastal stations. From May onwards both the maximum and minimum temperatures start falling, the latter very rapidly while the former slowly. Annual Mean minimum and mean maximum temperatures of various stations in Kerala from 1994-2003 are given in the table

The total annual rainfall in the State varies from 360 cm. over the extreme northern parts to about 180 cm. in the southern parts. The southwest monsoon (June­October) is the principal rainy season when the State receives about 70% of its annual rainfall. Monsoon rainfall as percentage of annual rainfall decreases from north to south and varies from 83 % in north most district of Kasaragode to 50% south most district of Thiruvananthapuram. Northeast monsoon rainfall as percentage of annual rainfall increases from north to south and varies from 9% in north most district ofKasaragode to 27% in south most district of Thiruvananthapuram. The rainfall amount in the State decreases towards the south with decrease of height of Western Ghats . The southern most district of Thiruvananthapuram where Western Ghats are nearest to the sea coast and its average height is also least in the State receives minimum amount of rainfall. The thunderstorm rains in the pre-monsoon months of April and May and that of monsoon months are locally known as 'EDAVAPATHI'. Rainfall during northeast monsoon season is known as 'THULAVARSHAM' in local language. The southwest monsoon sets -over the southern parts of the State by about 1 st June and extends over the entire State by 5 th June. June and July are the rainiest months, each accounting individually to about 23% of annual rainfall. Monthly distribution of Normal and Actual rainfall of Kerala state for last ten years are shown in Table

The diversity of the geographical features of the state has resulted in a corresponding diversity in climate. The High Ranges have a cool and bracing climate throughout the year, while the plains are hot and humid. The average level of annual rainfall is quite high when compared to other Indian states. The state basically enjoys 4 types of climate such as Winter, Summer, South West Monsoon and North East Monsoon.

Download District wise Annual Average Rainfall data from 2003 to 2008

The winter season sets in during the month of December and continues till end of February. During this season comparatively there is less rainfall especially in the northern parts of the state.

Winter is followed by the summer season. It starts in February and continues till May. Temperature is very high during this period. Occasional showers with Lightning is a characteristic of this season. Kottayam receives the highest rainfall during this season

The South West Monsoon begins either in the end of May or in the beginning of June and fades out by September. Moving towards north, this seems to gain intensity. During this period Peerumedu in Idukki and Vaithiri-Kuttiyadi range in Malabar receive the highest rainfall. The rainfall is comparatively low in the Lakshadweep islands. In the southern areas the monsoon is around 40-50% and in the northern areas it is around 80%.

The NorthEast Monsoon commences in October, dry weather setting in by the end of December. The Kanjirappalli-Peerumedu range and Kuttiyadi area experience the abundance of NorthEast Monsoon. The northern parts of the state account for a mere 10% of the annual rainfall.

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