India has received 19% less rain than average since the monsoon season began on June 1. (PTI file photo)

Monsoon rains were 35 percent below average in the week ending on Wednesday, with little rainfall over the central, western and northern parts of the country, the weather office said, raising concerns over the output of summer-sown crops.

Monsoon rains are crucial for farm output and economic growth as about 55% of the country's arable land is rain-supplied and agriculture forms about 15% of a $2.5 trillion economy that is the third biggest in Asia.

The biggest soybean growing central state of Madhya Pradesh received 67% less rainfall than average in the week, while top cotton producing Gujarat received 47% less, data from the India Meteorological Department (IMD) showed.

Overall, India has received 19% less rain than average since the monsoon season began on June 1.