South India is ending the monsoon season with one of the country's largest rainfall deficits, weather data shows.

The India Meteorological Department said conditions became favourable for the southwest monsoon's withdrawal from parts of west Rajasthan around September 19.

As of mid-September, the overall monsoon deficit stood at 15 percent. The south peninsula had the largest regional shortfall at 28 percent. East and northeast India were 25 percent below normal.

Among states, Andhra Pradesh recorded a 43 percent deficit. Karnataka was 29 percent short, Kerala 27 percent and Tamil Nadu 26 percent. Meghalaya had the highest deficit of any state at 59 percent.

IMD's long-range forecast had predicted below-normal rainfall for the season. It estimated all-India rain at 90 percent of the long-period average.

A weak monsoon can hurt farm output and water reserves in the south. Experts say reservoir levels and the winter crop will depend on the northeast monsoon that follows.

Weather watchers now wait to see how the retreating monsoon behaves in the coming weeks.