The key difference lies in their geographical locations. Kerala, being a coastal state, is greatly influenced by the Arabian Sea. The presence of a large water body moderates its climate, keeping temperatures less extreme and contributing significantly to high humidity. Rajasthan, on the other hand, is an inland desert region, far from the moderating influence of the sea. This geographical isolation leads to extreme temperatures (very hot summers and cold winters) and very low humidity due to the lack of moisture sources, creating its characteristic hot and dry climate. Altitude does not primarily explain the humidity difference, and equatorial proximity or sunlight are not the main differentiating factors here.