India, May 16 -- The southwest monsoon is expected to arrive over Kerala on May 26, nearly six days earlier than normal, according to the India Meteorological Department (IMD). The usual onset date is June 1.

An early arrival of monsoon generally brings hope of relief from heat and a good farming season. Nearly half of India's farmland depends on rainfall instead of irrigation.

Weather agencies and climate scientists, though, are warning that a developing El Nino pattern in the Pacific Ocean could weaken the overall monsoon later in the season.

The IMD said the monsoon is likely to set in over Kerala on May 26, with a model error margin of plus or minus four days. Last year too, the monsoon reached Kerala early, on May 24.

The weather...