The ocean remains cooler than the land, so the air above it stays at a higher pressure. This pressure difference causes moist air to blow from the ocean to the land, bringing rainfal

 The southwest monsoon is a seasonal wind system that brings heavy rains to the Indian subcontinent. It's characterized by the following features: 

An example 

When it occurs

The southwest monsoon usually begins in June and lasts until September. It typically arrives on the western coast of India near Thiruvananthapuram, and covers the entire country by mid-July. It usually starts to withdraw from India in early September and finishes by early October. 

How it occurs

The southwest monsoon is caused by the difference in temperature between the land and the ocean. The land heats up during the summer, causing the air above it to expand and create an area of low pressure. The ocean remains cooler than the land, so the air above it stays at a higher pressure. This pressure difference causes moist air to blow from the ocean to the land, bringing rainfall. 

Importance

The southwest monsoon is vital for agriculture and water resources in India. However, heavy rainfall can lead to flooding, while little or no rain can lead to drought and famine.