What is the reason behind the sudden heavy rain in Delhi-NCR?

The Delhi-NCR region experienced sudden heavy rainfall on Tuesday. Explaining the reason behind the sudden weather change, a senior scientist at IMD, Dr Naresh Kumar, said, "A low-pressure system...is forming in the Bay of Bengal and the Arabian Sea, causing the rain in...Delhi, and Uttar Pradesh." Kumar said that light rainfall will persist till Thursday in and around Delhi.