Why does Mumbai receive rainfall in summers while Chennai receives rainfall in winters?

Mumbai receives rainfall in the month of June to September because it lies on the west coast of India and Southwest monsoon rises from the Arabian Sea in the west. This monsoon brings moisture and causes rainfall in all parts of India in summer except Tamil Nadu, West Bengal and few more. By the time South-west monsoon reaches Chennai, it becomes offshore and causes very low rainfall. In October and November, Southwest Monsoon becomes weak and low-pressure trough, where trade winds converge move southward. This brings retreating monsoon in Tamil Nadu and some peninsular regions. These are the rainiest months of Chennai due to cyclonic depressions which comes in the Eastern Ghats and Eastern Coast.