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| Last Updated:: 09/11/2016

Climate

             The climate of Kerala, as per Koppen's classification, is tropical monsoon with seasonally excessive rainfall and hot summer except over Thiruvananthapuram district, where the climate as tropical savana with seasonally dry and hot summer weather. The entire state is classified as one meteorological sub division for climatologically purposes. The year may be divided into four seasons. The period March to the end of May is the hot season. This is followed by Southwest Monsoon season that continues till the beginning of October. From October to December is the Northeast Monsoon season and the two months January & February winter season. The climate is pleasant from September to February. Summer months March to May is uncomfortable due to high temperature and humidity. The State is extremely humid due to the existence of Arabian Sea in the west of it.

 

Wind: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.

 

Humidity: 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.

 

Temperature: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.

 

Rainfall: 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 (June­-October) 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 of Kasaragode 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 5th 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 .

                  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.

 

Winter Season in Kerala

                      In Kerala the winter season starts when the northeast monsoons ends. That is from the month November till the middle of February. During this time, the temperature is less but it does not have much difference with the other seasons. The temperature remains cool constantly throughout the year in the highlands but the winter temperatures falls below 10°C. It is during this winter season that we receive some of the lowest amount of rainfall.

Average Temperature during Winter in Kerala:

Maximum: 28°C 
Minimum : 18°C

Average Rainfall during the season :

25 mm

 

 

 

 

Summer Season in Kerala

                            The temperature starts to increase with the end of February which indicates the beginning of summer in Kerala. The characteristics of summer in Kerala are relatively higher temperature, less rainfall and humid weather.  The other Indian states have a temperature of about 40°C, whereas in Kerala it is comparatively cool and pleasant. It is mainly because of the presence of the Western ghats that prevents the northern wind from entering our state. The Arabian sea bordering us that gives a cool breeze which helps to make the temperature moderate. Another important feature of this season is the arrival of rain which is accompanied by thunder and lightening. The summer season extends from March till May or the beginning of June. It ends with the beginning of monsoon.

Average Temperature during  Summer  in Kerala:

Maximum : 36°C 
Minimum  : 32°C

Average Rainfall during the season :

135 mm

 

 

 

 

South West Monsoon in Kerala

                             The rainy season in Kerala is the Southwest monsoon. In malayalam this season is called as Edavappaathi which means in the middle of the malayalam month Edavam.  It is called so because the rain starts by the middle of this month that is the end of May or early June. The following two months have torrential rain. As Kerala lies on the windward side of the Western Ghats and is the first state to get hit by the monsoon winds, this state receives heavy rainfall. It is the monsoon that provides almost 85% of the rains. The slopes of the Western Ghats receive the highest amount of rain. The rivers get flooded by the monsoons. This season continues till the end of September.

Average Temperature during this season :

Maximum : 30°C 
Minimum  :19°C

Average Rainfall during the season :

2250-2500 mm

 

North East Monsoon in Kerala

                      The North east monsoon is also known as the Retreating Monsoon or the Reverse monsoons. This hits Kerala when the southwest monsoon winds take their return. These rains are called as Thulavarsham in malayalam because it rains during the malayalam month thulam. It comes in the month October and November and at times continues up to December. The main feature of this season is heavy rains during afternoon together with lightening and thunder. The days are usually warm and humid without much variation in temperature.

Average Temperature:

Maximum : 35°C 
Minimum  :  29°C

Average Rainfall during the season :

450-500 mm

 

               There has been a great change in the climatic condition of the Earth in the past few years. This has affected the weather conditions in Kerala also. 

 

Average monthly rainfall in Kerala

Month

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Rainfall (mm)

14.6

16.6

36.1

110.9

252.6

653.2

687.2

404.7

252.3

270.7

158.6

45.9

 

Monsoon 2012

                        The Pre monsoon rainfall received in the state from 1st  March 2012 to 31st May 2012 was normal with a departure of -19 percent from the normal. The actual rainfall received during the period was 308.5 mm. Ernakulam District recorded excess pre monsoon rainfall (23%) and Kannur District had scanty rainfall (-68% departure from normal). Normal rainfall was received in 7 districts of the state (Alappuzha, Idukki, Kollam, Kottayam, Pathanamthitta, Thrissur and Wayanad). Pre monsoon rains were deficient in 5 Districts (Kasargod, Kozhikkode, Malappuram, Palakkad and Thiruvanathapuram)

                        Southwest monsoon current advanced over the Andaman Sea on 23rd  May with a delay of about 3 days and set in over Kerala on 5th  June, 4 days later than its normal date of 1st  June. The actual rainfall received in Kerala during the South West Monsoon season (1st June to 30th September 2012) was 1551.3 mm as against the normal rainfall of 2039.6 mm which was -24 percent deficient. During the previous SW monsoon (2011) Kerala had received an actual rainfall of 2215.8 mm. Eleven districts in the state received deficient rainfall during 2012, while Kasaragod, Kannur and Kozhikkode districts normal rainfall. Deficiency in SW monsoon was highest in Wayanad District (-49%) followed by Thiruvananthapuram (-43%) which is shown in the figure below.

          

South West Monsoon received in Kerala during 1st June – 30th September 2012

 

                          During the North East Monsoon season 2012 ( 1st  October to 31st  December 2012) the state received 310.8 mm of rainfall as against 480.7 mm of normal rainfall which was deficient with a percentage departure of -35 percent from the normal. Twelve districts in Kerala received deficient rainfall during this season except Ernakulam and Kozhikkode which recorded normal rainfall. Percentage departure from the normal was highest in Alappuzha District (-54%) followed by Malappuram and Pathanamthitta districts and both showed a deviation of -51 percent from the normal rainfall, which is shown in the figure below. District wise rainfall distribution in the state during 2012 is given in the Table (District wise Actual Rainfall, Normal Rainfall and Percentage of Departure for the year 2012)

 

 

North East Monsoon received in Kerala during 1st October – 31st December 2012
 

 

 

Drought Situation 2012

During North East monsoon season the most affected districts during South West monsoon season ie. Thiruvananthapuram and Wayanad received comparatively more and distributed rainfall. But other districts still received less rainfall compared to normal. This adversely affected the second (Mundakan) crop of rice from which the farmers expected maximum yield. In addition to this Alappuzha district also suffered from salt water inundation. In North Kerala, Malappuram, Kasaragod and Palakkad were the most affected districts.

The deficiency of monsoons has affected the reservoir storage levels in major reservoirs in the state. The low levels of reservoir storage further narrows the chances of providing life saving irrigation to these crops and the end result will be extensive crop damage. The entire state has been declared as drought affected and a series of initiatives were proposed for implementation including restructuring loans with the support of commercial banks. Departments may prepare both short term and long term strategies for addressing drought situation. The restoration of tanks and ponds, basin wise management strategies for water management, micro irrigation and agronomic measures for improving water use efficiency needs to be implemented urgently.


Monsoon 2013

The pre monsoon rainfall received in the State from 1st March 2013 to 31st May 2013 was normal with a departure of -42 percent from the normal. The actual rainfall received during the period was 218.9 mm. All the Districts except Kottayam and Wayanad recorded deficient rainfall. The percentage departure from normal was highest in Palakkad (-56percent), Malappuram (-56 percent) and Thrissur ( -56 percent ) Districts.


                   South West monsoon current advanced over the Andaman Sea 3 days earlier than its normal date of 20th May and set in over Kerala on its normal date of 1st June. The South West monsoon covered the entire country by 16th June, about 1 month earlier than its normal date of 15th July. Out of the total 36 meteorological subdivisions, 14 subdivisions constituting 48 percent of the total area of the country received excess season rainfall, 16 subdivisions (38 percent of the total area of the country) received normal season rainfall and the remaining 6 subdivisions (14 percent of the total area of the country) received deficient season rainfall. Out of the total of 641 districts, 100 were affected by moderate meteorological drought (seasonal rainfall deficiency of 26 percent to 50 percent), while 39 were affected by severe meteorological drought (seasonal rainfall deficiency of 51 per cent to 99 per cent). The actual rainfall received in Kerala during the South West Monsoon season (1st June to 30th September 2013) was 2570.3 mm as against the normal rainfall of 2039.6 mm which was 26 percent excess. During the previous SW monsoon (2012) Kerala had received an actual rainfall of 1551.3 mm which was -24 percent deficient. During 2013 SW monsoon season, 10 districts in the State received excess rainfall and 4 districts viz. Wayanad, Thrissur, Pathanamthitta and Kasaragod had normal rainfall. Excess rainfall was maximum in Idukki District with 47 percent departure from normal. The graphical representation of South West Monsoon Rainfall received from 1st June – 30th Sept 2013 is shown below:

 

 

 

 

During the North East Monsoon season 2013 the State received 430.7 mm (till 18th  December  2013) of rainfall as against 473 mm of normal rainfall which was normal with a percentage departure of -9 percent. Five Districts in Kerala received deficient rainfall (Alappuzha: -33 percent, Kasaragod: -34 percent, Idukki: -20 percent, Palakkad: -26 percent, and Wayanad : -29 percent).  The  North East Monsoon Rainfall received from 1st  October to 18th  December 2013 is shown below and  district wise rainfall distribution in the state during 2013 is shown here

 

 

 

 Monsoon 2014

The pre monsoon rainfall which is received in Kerala during March to May was normal this year with a departure of -4 percent from normal. The actual rainfall in Kerala during pre monsoon season was 364.4mm, among the districts, Thiruvananthapuram and Wayanad received excess rainfall during this period and Thrissur experienced deficit rainfall. Lakshadweep showed a scanty condition in 2014 with percent departure of -67 from the normal.

Monsoon current advanced over the Andaman sea two days earlier than its normal date of 20th May. However, it set in over Kerala on 6th June, five days later than its normal date of 1st June and covered the entire country by 17th July, two days later than its normal date 15th July. Withdrawal of monsoon from west Rajasthan commenced on 17th September against its normal date of 1st September. Out of the total 36 meteorological sub divisions, 23 sub divisions consisting 67% of the total area of the country received normal season rainfall and 12 divisions (30% of the total area of the country) received deficient season rainfall. One subdivision (south interior Karnataka) consisting 3% of the total area of the country received the excess rain fall.  The actual rainfall received in Kerala during south west monsoon season (1st June to 30th September) was 2163.3mm as against the normal rainfall of 2039.7mm in 2014 showing +6percent departure from normal. There was an excess on 26 percent in the south west monsoon rainfall during 2013. This year all districts in Kerala received normal rainfall for south west monsoon season.

 South West monsoon Rainfall received from 1st June to 30th September 2014

 

During north east monsoon season the actual rainfall received in Kerala was 461.4mm as against the normal rainfall of 464.2mm among the districts Palakkad (-22%) received deficient rainfall whereas Ernakulum  (+21%) and Kottayam (+26%) received excess rainfall during the season.

Northeast monsoon rainfall Received from 1st October to 17th December 2014 

 

Monsoon 2015

The actual rainfall received in Kerala during southwest monsoon season (1st June to 30th September 2015) was 1514.3 mm as against the normal rainfall of 2039.7 mm in 2015 showing -26 per cent departure from normal. This year normal rainfall was received in Kannur, Kottayam and Thiruvananthapuram districts and rainfall received was deficient in all other districts in Kerala from southwest monsoon season. 

 

South West Monsoon Rainfall received from 1st June – 30th Sept 2015

 

 

 During north east monsoon season the actual rainfall received in Kerala was 610.1 mm as against the normal rainfall of 480.7 mm showing excess rainfall from normal (+27%). Among the districts, Idukki, Kollam, Palakkad and Wayanad districts received normal rainfall and all other districts received excess rainfall during the season. District wise rainfall distribution in the State during North East Monsoon season 2015 is given as here

North East Monsoon Rainfall received from 1st October to 31st December 2015

 

 

 

Source

Economic Review 2013-2015,  IMD Thiruvananthapuram