* Likely to prompt earlier planting of some crops
* But overall monsoon rainfall expected to be just below average
* Monsoon is lifeblood of Indian economy
Monsoon rains hit the southern Indian state of Kerala a few days earlier than normal on Tuesday, the country's weather office said, potentially brightening the country's outlook for agricultural output and economic growth.
Monsoons deliver about 70% of India's annual rainfall and are the lifeblood of its $2.5tn economy, spurring farm output and boosting rural spending on items ranging from gold to cars, motorcycles and refrigerators.
"The southwest monsoon has set in over the southern state of Kerala, three days ahead of its normal date," the state-run India Meteorological Department (IMD) said in a statement.
The early arrival of monsoon rains typically enables farmers to bring forward sowing of crops such as rice, sugarcane, corn, cotton and soybeans because nearly half the country’s farmland lacks irrigation.
However, IMD Monsoon Director General K.J. Ramesh last month forecast that monsoon rains were expected to be 97% of a long-term average.
India's weather office defines average, or normal, rainfall as between 96% and 104% of a 50-year average of 89 cm for the entire four-month season beginning June.
Other than boosting farm output and wider economic growth, a spell of roughly average rains could help keep a lid on inflation, potentially tempting Prime Minister Narendra Modi to bring forward a general elections due in May 2019.
Monsoon rains are likely to be unaffected by the El Nino weather pattern, which is expected to set in only after the four-month rainy season ends in September.
In 2017, monsoon rains were 95% of the long-term average compared to forecasts of 98%.
Before receiving average rains in 2016, India suffered back-to-back drought years for only the fourth time in more than a century, hurting incomes and driving some farmers to suicide.
Average monsoon rainfall would help India retain its position as the world's top rice exporter, but could further stoke a glut in supply of sugar.