The state has three principal geographical zones:
- the coastal region of Karavali
- the hilly Malenadu region comprising the Western Ghats
- the Bayaluseeme region comprising the plains of the Deccan plateau
The bulk of the state is in the Bayaluseeme region, the northern part of which is the second-largest arid region in India. The highest point in Karnataka is the Mullayanagiri hills in Chickmagalur district which has an altitude of 1,929 metres (6,329 ft). Some of the important rivers in Karnataka are Kaveri, Tungabhadra, Krishna, Malaprabha and the Sharavathi.
Karnataka consists of four main types of geological formations — the Archean complex made up of Dharwad schists and granitic gneisses, the Proterozoic non-fossiliferous sedimentary formations of the Kaladgi and Bhima series, the Deccan trappean and intertrappean deposits and the tertiary and recent laterites and alluvial deposits. Significantly, about 60% of the state is composed of the Archean complex which consist of gneisses, granites and charnockite rocks. Laterite cappings that are found in many districts over the Deccan Traps were formed after the cessation of volcanic activity in the early tertiary period. Eleven groups of soil orders are found in Karnataka, viz. Entisols, Inceptisols, Mollisols, Spodosols, Alfisols, Ultisols, Oxisols, Aridisols, Vertisols, Andisols and Histosols. Depending on the agricultural capability of the soil, the soil types are divided into six types, viz. Red, lateritic, black, alluvio-colluvial, forest and coastal soils.
Karnataka experiences four seasons. The winter in January and February is followed by summer between March and May, the monsoon season between June and September and the post-monsoon season from October till December. Meteorologically, Karnataka is divided into three zones — coastal, north interior and south interior. Of these, the coastal zone receives the heaviest rainfall with an average rainfall of about 3,638.5 mm (143 in) per annum, far in excess of the state average of 1,139 mm (45 in). Agumbe in the Shivamogga district receives the second highest annual rainfall in India. The highest recorded temperature was 45.6 °C (114 °F) at Raichur and the lowest recorded temperature was 2.8 °C (37 °F) at Bidar.
About 38,724 km2 (14,951 sq mi) of Karnataka (i.e. 20% of the state's geographic area) is covered by forests. The forests are classified as reserved, protected, unclosed, village and private forests. The percentage of forested area is slightly less than the all-India average of about 23%, and significantly less than the 33% prescribed in the National Forest Policy.