India's monsoon rains advanced into some more parts of southwest Bay of Bengal after stalling for the past 11 days at a far-flung island, weather department said on Tuesday.

The monsoon, the lifeblood of the country's $3 trillion economy, delivers nearly 70% of the rain that India needs to water farms and recharge reservoirs and aquifers.

Nearly half of India's farmland, without any irrigation cover, depends on the annual June-September rains to grow a number of crops.

Monsoon rains arrived over the remote Andaman and Nicobar Islands on May 19, but then didn't make any progress until May 30, the India Meteorological Department (IMD) said.

Monsoon advanced into some parts of southwest Bay of Bengal on Tuesday and conditions are favourable for further advance into more parts of the region during the next 2-3 days, the IMD said.

Rains usually lash mainland Kerala around June 1 and cover the whole country by mid-July. Timely rains trigger planting of crops such as rice, soybeans and cotton.

This year, the onset of the monsoon over Kerala is likely to be slightly delayed. The onset of monsoon rains over the southern Indian state is likely to be on June 4, with a model error of plus/minus 4 days.