According to bridgat, the climate of India is determined by several factors: first of all by the tropical position of the country, then by its opening to the Indian Ocean and by the presence of the Himalayan range at N. However, not all of the territory has similar conditions. The relief is a first factor of diversification, to which are added the latitude and the more or less direct exposure to the invasions of large air masses. In fact, there is an arid India, an India with a distinctly two-season climate, an India with a humid equatorial climate, not to mention the Himalayan climate with very special characteristics. Overall, however, there are no major anomalies in the country. From a thermal point of view, the opening to the Indian Ocean means that the variations are almost exclusively related to the relief, continentality, which also makes itself felt on seasonal variations, more sensitive towards the N and towards the interior. In Delhi the average in January is 15 ºC, that of July 22 ºC; in Kolcata and Mumbai the same averages are respectively 20 ºC and 28 ºC and 24 ºC and 28 ºC (Mumbai is more excluded from the continental influences than Kolcata); in Chennai, in the southern Deccan, the averages are 25 ºC and 31 ºC while in Kozhikode (Calicut), an area with an equatorial climate, the values are almost constant all year round (26 ºC and 25 ºC).
On the other hand there are the considerable variations of the Himalayan zone, mirrored in the averages of Srinagar, equal to 2 ºC in January and 24 ºC in July. The distribution of precipitation is much more irregular. In fact, there are decidedly arid areas in India, such as Rajasthan, and others where there is some of the highest rainfall on Earth, such as Assam. However, much of the country has rainfall of between 500 and 1500 mm; however, they occur in a single season and this, more than the quantity of rains, constitutes a negative aspect, especially in certain regions, of the Indian climate. This is in fact generally of the tropical type with two seasons, linked to the expiration of the gods monsoons. In the summer, as temperatures rise, low pressures are determined on the country, while an anticyclonic zone is established on the Indian Ocean and winds from the SW, carried by the masses of tropical air. After a period of suffocating heat which in many places recorded the maximum values of the temperature (up to 50 ºC in Rajasthan) the rains begin, often accompanied by violent storms, and the temperature cools down. This occurs in southern India in early June and towards the end of the month the monsoon also spreads in the N and NW where it gradually weakens: this explains the aridity of the areas included in the Indus basin. In mid-September the SW monsoon loses vigor and rainfall decreases, even in the southern areas most exposed to marine influences.
Thus we have a hot and dry season that marks the barometric inversion, with the imposition of the continental winds from the NE (or in certain areas, as in the Gangetic plain, from the NW) attracted by the low pressures in the equatorial belt of the Indian Ocean. In the South, however, there is still precipitation due to the characteristic equatoriality of the western coastal strip. This is where the maximum rainfall of the Deccan occurs: in Kozhikode they exceed 3000 mm per year, a value that decreases towards the North up to 1700 mm in Mumbai. In the interior of the peninsula the values fluctuate between 1000 and 1200 mm, and increase in the southern slopes of the Central Highlands. In Assam the high values of precipitation (over 5000 mm per year) are due to the summer stationing of in Kozhikode they exceed 3000 mm per year, a value that decreases towards the north up to 1700 mm in Mumbai. In the interior of the peninsula the values fluctuate between 1000 and 1200 mm, and increase in the southern slopes of the Central Highlands. In Assam the high values of precipitation (over 5000 mm per year) are due to the summer stationing of cyclones in the Bay of Bengal, cyclones that hit the region directly, often with a violence that has particularly disastrous consequences on the coasts of Bangladesh, especially in the Chittagong belt. Also in Bengal there is abundant rainfall and in Kolcata over 1600 mm of rain fall annually. The values decrease from E to W in the Ganges plain, where moreover the rains are very irregular (in Delhi there are 660 mm per year); in the arid lands of Rajasthan, 250 mm per year are generally not exceeded, while in the far north Srīnagar is more favored, which being on the Himalayan side also receives over 600 mm of water per year. The seasonal alternation leaves much of India dry for long months and this corresponds to a period of pause of the same human activity, which is suddenly revived by the first manifestations of the monsoon. Sometimes these are slow in coming and there are then in certain areas (frequently in the northern plain) dramatic famines.