Indian monsoon deficit: what's the cause?

The Indian monsoon season spans from June to September and brings much needed rain to the region after months of sweltering heat.

Indian agriculture is dependent on the climate of India and a favourable summer monsoon is absolutely critical for securing water for irrigating crops.

As the monsoon began its retreat in September, the India Meteorological Department confirmed that India as a whole, has suffered a rainfall deficit of 12-15%, with some regions experiencing a deficit of almost 50%.

This kind of deficit is around 1 in 18 year event.

What is the cause and what will the impact be on India? BBC Weather's Nick Miller explores further.