NEW DELHI, Sept 30 (Reuters) - India's rainfall was 14 percent lower than normal in the June-September monsoon season, provisional data posted on the website of Indian Metrological Department showed on Wednesday.

The weather office had forecast a 12 percent rain deficit in the four-month long season.

That makes this the first back-to-back drought for India in three decades, and only the fourth in more than a century. The scant rains have hit the yields of summer-sown crops, especially in the south of the country.

Monsoon rains have been below average levels due to El Nino, a weather pattern caused by Pacific Ocean warming that can lead to droughts in South Asia.

In some regions the rainfall deficit during the season was as high as 47 percent, resulting in shortages of drinking water.

(Reporting by Rajendra Jadhav, Writing by Nidhi Verma; Editing by Douglas Busvine) ((nidhi.verma@thomsonreuters.com; +91 11 4178 1018; Reuters Messaging: nidhi.verma.thomsonreuters.com@reuters.net))