The state of Karnataka is part of two well-defined regions of India, namely the Deccan Plateau and the Coastal Plains and Islands and it can be further divided into four physiographic regions-the Northern Karnataka Plateau, Central Karnataka Plateau, Southern Karnataka Plateau, Karnataka Coastal Region. The Central Karnataka Plateau is the area between the Northern and Southern Karnataka Plateaus, which results in the general elevation varying between 450 and 700 meter. This region represents the area of the Tungabhadra basin. Central Karnataka Plateau covers the districts of Bellary, Chikmagalur, Chitradurga, Dharwad, Raichur and Shimoga. The general slope of this region is towards the east.
Northern Karnataka Plateau
The Northern Karnataka Plateau, at an elevation of 300 to 600 meter, is largely composed of the Deccan Trap. It represents a monotonous, treeless extensive plateau landscape rich in black cotton soils. Northern Karnataka Plateau comprises of the districts of Belgaum, Bidar, Bijapur and Gulbarga and is largely composed of the Deccan Trap. However the river plains of the Krishna, the Bhima, the Ghataprabha and the Malaprabha with the intervening watersheds, the step like landscapes, lateritic scarpments, residual hills and ridges break the monotony of this extensive plateau. The general slope is towards the east. This region is largely covered with rich black cotton soils.
Central Karnataka Plateau
Southern Karnataka Plateau
The Southern Karnataka Plateau covers the area of the Cauvery river basin lying in Karnataka and is encircled by the Western Ghats in the west and south. In the east the valleys of the Cauvery and its tributaries open out to form undulating plains. The region is situated between 600 and 900 meter above sea level. However, residual heights of 1,500 to 1,750 metres are found in the Biligirirangan hills of Mysore district and the Brahmagiri range of Kodagu district. The Southern Karnataka Plateau covers the districts of Bangalore, Bangalore Rural, Hassan, Kodagu, Kolar, Mandya, Mysore and Tumkur. It is bounded by 600 metres contour and is characterised by a higher degree of slope.
Karnataka Coastal Region
The Karnataka Coastal Region, which extends between the Western Ghats, edge of the Karnataka Plateau in the east and the Arabian Sea in the West, covers Dakshina Kannada and Uttara Kannada districts. This region is traversed by several ridges and spurs of Western Ghats. It has difficult terrain full of rivers, creeks, water falls, peaks and ranges of hills. The coastal region consists of two broad physical units, the plains and the Western Ghats. The Coastal plains, represent a narrow stretch of estuarine and marine plains. The abrupt rise at the eastern flanks forms the Western Ghats. The northern parts of the ghats are of lower elevation (450-600 metres) as compared to Southern parts (900 to 1,500 metres). The Coastal belt with an average width of 50 to 80 km covers a distance of about 267 km. from north to south.
The state boasts of a wide range of topological features. There are chains of mountains, the highest being the Mullayyana Giri (1,925m). Other than the mountains, there are plateaus, residual hills and coastal plains. Among the tallest peaks of Karnataka are the Mullayyana Giri (1,925 m), Bababudangiri (Chandradrona Parvata 1,894 m) and the Kudremukh (1,895 m) all in Chikmagalur Dt. and the Pushpagiri (1,908 m) in Kodagu Dt. There are a dozen peaks which rise above the height of 1,500 metres.
The state enjoys three main types of climates.
The Tropical Monsoon climate covers the entire coastal belt and adjoining areas. The climate in this region is hot with excessive rainfall during the monsoon season i.e., June to September. The Southern half of the State experiences hot, seasonally dry tropical savana climate while most of the northern half experiences hot, semi-arid, tropical steppe type of climate. The climate of the State varies with the seasons.
The winter season from January to February is followed by summer season from March to May. The period from October to December forms the post-monsoon season. The period from October to March, covering the post-monsoon and winter seasons, is generally pleasant over the entire State except during a few spells of rain associated with north-east monsoon which affects the south-eastern parts of the State during October to December.
The months April and May are hot, very dry and generally uncomfortable. Weather tends to be oppressive during June due to high humidity and temperature. The next three months (July, August and September) are somewhat comfortable due to reduced day temperature although the humidities continue to be very high.
Both day and night temperatures are more or less uniform over the State, except at the coastal region and high elevated plateau. They generally decrease south-westwards over the State due to higher elevation and attain lower values at high level stations. April and May are the hottest months. In May, mean maximum temperature shoots upto 40 deg. C over the north-eastern corner of the State, decreasing south-westwards towards the Western Ghat region and the Coastal belt.
The highest temperature recorded at an individual station in the State is 45.6 deg. C at Raichur on 1928 May 23, which is 6 deg. higher than the normal for the warmest months. December and January are the coldest months. The lowest temperature at an individual station was 2.8 deg. C on 1918 December 16 at Bidar.
The annual rainfall in the State varies roughly from 50 to 350 cm. In the districts of Bijapur, Raichur, Bellary and southern half of Gulbarga, the rainfall is lowest varying from 50 to 60 cm. The rainfall increases significantly in the western part of the State and reaches its maximum over the coastal belt. The south-west monsoon is the principal rainy season during which the State receives 80% of its rainfall. Rainfall in the winter season (January to February) is less than one per cent of the annual total, in the hot weather season (March to May) about 7% and in the post-monsoon season about 12%.
South-West monsoon normally sets in over the extreme southern parts of the State by about 1st of June and covers the entire State by about 10th of June. The rainy months July and August account individually to about 30% and 18% of annual rainfall. There are about 26 rainy days (with daily rainfall of atleast 2.5 mm) in the south-west monsoon begins from the northern parts of the State around 2nd week of October and by the 15th October monsoon withdraws from the entire State.
The retreating monsoon current i.e. the north-east monsoon (October to December) effects the eastern parts of South Interior Karnataka and accounts for about 30% of rainfall in this region. Out of the 14 heavy rainfall stations in India, with annual rainfall of more than 500 cm., four stations are situated in Karnataka. They are Agumbe in Tirthahalli taluk of Shimoga district (annual rainfall-828 cm) and Bhagamandala (603 cm), Pullingoth (594 cm) and Makut (505 cm) in Kodagu district.
Best time to visit
The variation in the geographical features affects the climate of the region. Coastal Karnataka experiences a hot, rainy tropical monsoon climate. In the southern inland places the climate is hot and dry and the interior northern areas are semi arid and hot. Best time to visit Karnataka is between September and February.