The India Meteorological Department (IMD) has indicated that the retreat of the southwest monsoon from central India may be delayed this year due to the formation of fresh weather systems over the Bay of Bengal.

The southwest monsoon's withdrawal typically begins in mid-September, starting from northwest India and progressively retreating southwards. The transition from moist oceanic air masses to dry continental air masses dictates the monsoon's onset and retreat. The presence of weather systems in the Bay of Bengal can disrupt this process, potentially causing a delay in the monsoon's retreat from central India. These systems can draw moisture from the Arabian Sea and the Bay of Bengal, leading to continued rainfall activity over parts of India.

The monsoon is a complex weather system influenced by various factors, including the interaction of monsoon maritime air masses with mid-latitude westerly disturbances, which can alter rainfall distribution. For instance, in January 2025, a western disturbance interacting with moist tropical air resulted in unseasonal rain in Punjab. The Arabian Sea and Bay of Bengal air masses also create regional disparities in rainfall, with northeastern states receiving over 2000 mm of rainfall while Rajasthan remains semi-arid.

This year, North India experienced an unusual overlap of weather systems, where monsoon lows from the Bay of Bengal were pushed further north by moisture-laden winds from the Arabian Sea, converging with a greater number of Western Disturbances. These interactions enhanced lift and instability, amplified by a northward-shifted low-level jet carrying Arabian Sea moisture into North India.

The IMD has maintained a high level of accuracy in forecasting monsoon rainfall in recent years. Accurate forecasts are crucial for planning in various sectors, including agriculture, water management, and disaster preparedness. The monsoon is particularly vital for crops like rice, cotton, and sugarcane, and any delays or failures can significantly impact food supply, livelihoods, and the economy.

However, despite the overall "normal" classification, some regions may experience rainfall deficiencies. As of September 15, 2025, Kerala had received 1,612.6 mm of rainfall against the seasonal average of 1,888.2 mm, a shortfall of 15%. Shortfalls are expected to widen slightly, and the tentative latitude of weather systems in the Bay of Bengal isn't favorable for triggering intense spells in Kerala over the next two weeks. Light to moderate and short-lived spells are expected to continue.

The changing patterns of the monsoon, influenced by climate change, also bring challenges. There's a shift from steady, season-long rains to long dry spells interspersed with intense bursts, with a warmer atmosphere carrying more moisture and resulting in exceptionally heavy rainfall when storms occur.