India is bracing for an early monsoon in 2025, with the India Meteorological Department (IMD) forecasting the onset over Kerala by May 27. This marks the earliest arrival of the southwest monsoon on the Indian mainland since 2009 when it arrived on May 23. The usual date for the monsoon to hit Kerala is around June 1st, making this a notably early start to the rainy season.
The early arrival is attributed to a rare convergence of climatic variables. One key factor is the early formation of an east-west shear zone, a belt of atmospheric instability that typically appears in late May but materialized by mid-May this year. This has triggered low-pressure systems in both the Arabian Sea and the Bay of Bengal, classic indicators of an advancing monsoon. Additionally, an intensifying cyclonic circulation over the southeast Arabian Sea is drawing in moist monsoon winds toward the southern peninsula. Neutral El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) conditions are also contributing to the favorable monsoon conditions.
The IMD has predicted above-normal rainfall for the 2025 monsoon season, exceeding 104% of the Long Period Average (LPA). This is welcome news for India, where the monsoon plays a crucial role in agriculture, water supply, and the overall economy. A good monsoon is particularly vital for Kharif crops like rice, cotton, and pulses, and is expected to keep food prices stable, barring any localized flood damage or erratic rainfall in August.
While the early onset is generally seen as positive, some concerns remain. The formation of twin cyclonic systems in the Arabian Sea and the Bay of Bengal introduces uncertainty. These systems could potentially lead to a stalling of monsoon winds, a phenomenon observed in previous years. In 2024, for example, the Bay of Bengal branch of the monsoon stalled for 19 days due to Cyclone Remal, leading to higher-than-normal temperatures and even heat waves in some regions. A similar situation occurred in 2021 with Cyclones Tauktae and Yaas.
Despite these uncertainties, many parts of India are already experiencing pre-monsoon showers and thunderstorms. A yellow alert has been issued for Mumbai and other parts of Maharashtra, warning of thunderstorms, lightning, moderate rainfall, and gusty winds. The IMD has also issued an orange alert for several districts in Kerala due to heavy rains.
The early monsoon onset is also impacting temperatures across the country. Tamil Nadu, for example, is witnessing conditions more typical of early June than mid-May, with no heat waves reported so far this year and Chennai's temperatures staying below 40°C. Mumbai has also experienced unusually early pre-monsoon showers, with rainfall totals already close to levels not seen since the early 2000s.
As the monsoon progresses, the IMD is closely monitoring the situation and emphasizing the importance of preparedness. The early onset is expected to bring much-needed irrigation to western belts and boost early-season farming in Tamil Nadu, while Mumbai is preparing for monsoon around June 5-7. While the exact impact of the early monsoon remains to be seen, the current conditions suggest a strong and active rainy season for India in 2025.
