Southwest monsoon likely to reach Andaman Sea ahead of schedule this week

The southwest monsoon is likely to advance into parts of the Andaman Sea and the Andaman and Nicobar Islands later this week, with the India Meteorological Department indicating that conditions are becoming favourable for its onset over the region.

In its daily weather bulletin issued on Tuesday, the IMD said the southwest monsoon is likely to set in over parts of the south Bay of Bengal, the Andaman Sea and adjoining islands towards the end of the week.

If the forecast materialises, the onset over the south Andaman Sea would occur around five to six days ahead of the normal schedule. Last year, the monsoon reached the region on 13 May. Climatologically, the normal date for monsoon onset over the Andaman Sea region is around 22 May.

The advance of the monsoon into the Andaman region is considered the first major indicator of the seasonal progression of the southwest monsoon towards mainland India. The normal onset date over Kerala is 1 June, marking the formal beginning of the country’s four-month rainy season.

However, meteorologists have repeatedly stressed that an early onset over the Andaman Sea does not necessarily indicate either an early arrival over mainland India or above-normal seasonal rainfall.

Low-pressure system developing over Bay of Bengal

The IMD on Monday had also reported the formation of a low-pressure area over the southwest Bay of Bengal. According to the weather department, the system continues to persist over the region and is expected to intensify over the next 48 hours.

The department said a cyclonic circulation associated with the low-pressure system is also active over the area, aiding favourable conditions for the monsoon’s advance.

The southwest monsoon remains India’s principal rainy season and contributes more than 70 per cent of the country’s annual rainfall between June and September. The country’s long-period average seasonal rainfall stands at around 880 mm.

Monsoon rainfall plays a critical role in agriculture, groundwater recharge, reservoir storage and hydropower generation, and is closely linked to India’s overall economic activity and rural consumption patterns.

IMD had forecast below-normal rainfall

In its first-stage Long Range Forecast released in mid-April, the IMD projected below-average monsoon rainfall for 2026. The department estimated seasonal rainfall at around 92 per cent of the long-period average for the 1971–2020 period.

A below-normal monsoon can raise concerns over agricultural output, food inflation and water availability, particularly in rain-fed regions of the country.