Goa encompasses an area of 3,702 km² (1,430 sq mile). It lies between the latitudes 14°53′54″ N and 15°40′00″ N and longitudes 73°40′33″ E and 74°20′13″ E. Most of Goa is a part of the coastal country known as the Konkan, which is an escarpment rising up to the Western Ghats range of mountains, which separate it from the Deccan Plateau. The highest point is the Sonsogor, with an altitude of 1,167 meters (3,827 feet). Goa has a coastline of 101 km (63 miles).
Goa's main rivers are the Mandovi, the Zuari, the Terekhol, Chapora River and the Sal. The Mormugao harbour on the mouth of the River Zuari is one of the best natural harbours in South Asia. The Zuari and the Mandovi are the lifelines of Goa, with their tributaries draining 69% of its geographic area. These rivers are some of the busiest rivers in India. Goa has more than forty estuarine, eight marine and about ninety riverine islands. The total navigable length of Goa's rivers is 253 km (157 miles). Goa has more than three hundred ancient tanks built during the rule of the Kadamba dynasty and over a hundred medicinal springs.
Most of Goa's soil cover is made up of laterites which are rich in ferric aluminium oxides and reddish in colour. Further inland and along the riverbanks, the soil is mostlyalluvial and loamy. The soil is rich in minerals and humus, thus conducive to plantation. Some of the oldest rocks in the Indian subcontinent are found in Goa betweenMolem and Anmod on Goa's border with Karnataka. The rocks are classified as Trondjemeitic Gneiss estimated to be 3,600 million years old, dated by the Rubidiumisotope dating method. A specimen of the rock is exhibited in the Goa University.
Goa features a tropical monsoon climate under the Koppen climate classification. Goa, being in the tropical zone and near the Arabian Sea, has a hot and humid climate for most of the year. The month of May is the hottest, seeing day temperatures of over 35 °C (95 °F) coupled with high humidity. The monsoon rains arrive by early June and provide a much needed respite from the heat. Most of Goa's annual rainfall is received through the monsoons which last till late September.
Goa has a short winter season between mid-December and February. These months are marked by nights of around 21 °C (68 °F) and days of around 28 °C (84 °F) with moderate amounts of humidity. Further inland, due to altitudinal gradation, the nights are a few degrees cooler. During March 2008 Goa was lashed with heavy rain and strong winds. This was the first time in 29 years that Goa had seen rain during March.