Monsoons happen because of a simple fact: land heats up faster than water. The temperature difference between the land and sea can be as much as 20°C – land temperatures in India can be hotter than 45°C, while the surrounding water in the Bay of Bengal and the Arabian Sea remains in the low 20s. The heat absorbed by the land warms the air above it. The hot air rises, and cooler ocean air rushes inland to replace it. As it moves, it carries moisture with it, releasing it over land as the summer monsoon (also known as southwest monsoon). 