Thiruvananthapuram: The Indian Meteorological Department (IMD) on Thursday officially declared the onset of the southwest monsoon over Kerala, signaling the start of the country’s four-month rainy season.

The monsoon reached the state on June 4, three days later than the usual onset date of June 1.

According to the IMD, the southwest monsoon has advanced into the remaining parts of the southwest and southeast Arabian Sea, the entire Lakshadweep region, Kerala, and Mahe. It has also covered parts of Karnataka and Tamil Nadu, the remaining areas of the Kanyakumari region, and sections of the south, southwest, central, and northeast Bay of Bengal.

The Met Department said conditions remain favourable for the further advancement of the monsoon over the next two to three days. It is likely to spread into more parts of the central Arabian Sea, the whole of Goa, parts of Maharashtra and Andhra Pradesh, additional areas of Karnataka, the remaining parts of Tamil Nadu, the central and northeastern Bay of Bengal, and parts of northeast India. According to the IMD, the declaration was based on several favourable atmospheric changes observed during the past two days. A significant increase in dense cloud cover was recorded over the southeast Arabian Sea, and the depth of westerly winds over the region extended up to 4.5 km above mean sea level, indicating strengthening monsoon circulation.

Wind in the lower levels of the atmosphere also increased to around 20-25 knots, meeting one of the key criteria for declaring monsoon onset.

The IMD noted that widespread rainfall was recorded across Kerala over the last two days, with isolated places receiving heavy rainfall. The onset of the southwest monsoon over Kerala is closely watched each year as it marks the start of the rainy season across much of India and plays a crucial role in agriculture, water resources, and the broader economy.