The southwest monsoon, which accounts for more than 75% of India’s annual rainfall, has officially made landfall over Kerala—marking its earliest arrival in 16 years. The last time the monsoon hit the Indian coast this early was in 2009, when it arrived on May 23.
This early onset follows days of heavy rainfall across southern India. Kerala, Tamil Nadu, and much of Karnataka have been experiencing a sustained wet spell since last week. According to the India Meteorological Department (IMD), widespread rainfall is expected to continue in Kerala-Mahe and Karnataka until May 27–29. Meanwhile, Telangana, Tamil Nadu, Andhra Pradesh, and Rayalaseema are also forecast to receive heavy showers over the next five days, with warnings for extremely heavy rainfall on May 25 and 26.
Typically, the monsoon sets in over the southern coast around June 1. However, actual onset dates depend on atmospheric and oceanic conditions. This year, the IMD had predicted an early arrival around May 27 (±4 days), given favorable weather patterns. Surprisingly, the monsoon arrived even earlier—eight days ahead of the usual date.
While an early onset doesn’t guarantee above-average seasonal rainfall, it brings timely relief to farmers preparing their fields for sowing Kharif crops such as paddy. The agricultural sector is also buoyed by the IMD’s long-range forecast, which predicts an above-normal monsoon for 2025. Rainfall is expected to be at least 105% of the long-period average (LPA), which stands at 87 cm based on data from 1971 to 2020, with a model error margin of ±5%.
The southwest monsoon is vital to India’s agrarian economy, delivering the bulk of its annual rainfall in the four-month window from June to September. After its onset in Kerala, it generally takes more than a month to advance across the rest of the country, typically reaching its northernmost extent by July 8.
The IMD follows specific criteria, established in 2016, to announce the monsoon onset. These criteria include consistent rainfall across designated areas, sufficient rainfall strength, and prevailing wind velocities. For Kerala, the monsoon onset is confirmed if at least 60 percent of 14 designated stations record 2.5 mm or more rainfall for two consecutive days following May 10. These stations include Minicoy, Amini, Thiruvananthapuram, and several others.
The early monsoon arrival brings relief from the severe heatwave conditions in India. The expected above-normal rainfall due to the potential La Nina development will be beneficial for agriculture and water resources. However, the current heatwave highlights the need for preparedness and adaptive measures to mitigate the impacts of extreme weather conditions.
