The end of the rain-giving Summer Monsoon is being awaited in India now that September is nearing the halfway mark.

As of Monday, the India Meteorology Service (IMD) had not yet called an end to the Monsoon in the northwestern India, where the Monsoon normally ends first.

The IMD have assessed seasonal rainfall, nationwide, at near normal (within 1 percent weighted average) as of early September, with less than one month left in the official Summer Monsoon remaining.

Distribution of rainfall within India, however, has varied substantially. For example, rain shortfalls in the populous northeastern states of West Bengal, Jharkhand, Bihar and Uttar Pradesh have raised concerns for agriculture and water supply.

In contrast, stretches of southern, central and desert northwest India have benefited from above-normal rainfall.

Map showing normal withdrawal dates for the India Summer Monsoon. Map credit: India Meteorology Department. The vast weather system known as the Indian Summer Monsoon normally begins near the first of June in Sri Lanka and southern India, reaches its fullest extent over the Subcontinent in July, then begins its withdrawal towards the south and east starting with Pakistan near the first of September.

By the middle of September, rains of a summer Monsoon have normally yielded to dryness over much of northwestern India, especially in the state of Rajasthan.

The start of October marks the official end of the Summer Monsoon on the Subcontinent, although a fall Monsoon follows in southern India and Sri Lanka.

The IMD deem the Monsoon to have ended based upon a few objective criteria based upon rainfall, pressure patterns and moisture content of the atmosphere.

For example, five continuous days of rain-free weather in a given are would satisfy the first of these criteria.

Story by Jim Andrews, Senior Meteorologist