India has a tropical monsoon climate driven by the seasonal reversal of winds. The south-west monsoon arrives in Kerala around 1 June, advances across the country by mid-July, and retreats from September.
The monsoon splits into the Arabian Sea and Bay of Bengal branches. The windward Western Ghats receive very heavy rain while the leeward Deccan interior lies in a rain-shadow, which explains the sharp rainfall contrast over short distances.
The retreating monsoon brings rain to Tamil Nadu's coast in October and November. Mawsynram and Cherrapunji in Meghalaya are among the wettest places on earth.