India expects monsoon rainfall to be average in 2013, making it likely that one of the world's biggest producers of grains will avoid any widespread droughts for a fourth straight year.
The rains, vital for the roughly 55% of India's farmland that lacks irrigation, can swing the country from exporter of farm commodities to importer, or vice-versa.
About 800 million people live in rural parts of India and many depend on agriculture for their livelihood.
How much rain is enough?
India considers as normal, or average, a monsoon that brings rainfall between 96% and 104% of a 50-year average of 89 cm. in the entire four-month rainy season from June 1.
Even if rains are average, some areas could still have drought. Some Southern and Western states that got hardly half their normal rainfall in 2012 are still battling drought.
The last widespread drought in 2009 hit sugar output so badly that India's subsequent imports drove global prices to a 30-year high.
On the other hand, rains of more than 110% of the average would mean an excessive monsoon - not as damaging as drought but potentially hurting yields of lentils and rice.
The rains usually arrive in Kerala on the South coast around June 1, and cover the whole country by mid-July. Their progress triggers planting of crops such as rice, soybean and cotton.
The monsoon spreads from the tropical South to cover almost the entire sub-continent, a land mass of 3.29 million sq km that stretches to the Himalayan mountains in the north.
Within a week of arrival, the rains spread over the coffee, tea and rubber growing areas of the South. In the first 10 days they will have reached the rice-planting Eastern regions, including the top rice growing state, West Bengal.
Half the country is usually covered in the first 15 days. The rains get to central India's soybean areas by the third week of June and reach Western cotton-growing areas by the first week of July.
Crops planted in June and July contribute half of India's farm output. The summer rains also influence winter crops, such as wheat and rapeseed, grown in irrigated areas that depend on reservoirs filled by the rain.
Key crops and exports
Rice: Farmers sow paddy at the June start of the monsoon in the key Eastern and Southern regions.
India produced 102 million tonnes of rice in the crop year till June 2013, the farm ministry says, against annual consumption of around 90 million.
India allows unrestricted export of rice. Buyers are mostly in Africa and the Middle East, while the United States and Europe buy high-grade varieties.
Sugar: India is expected to produce a total of 24.3 million tonnes in the year to September 30, 2013, higher than annual demand of up to 23 million, but output may fall as low as 20 million in 2013-14.
India exported sugar in the last two years, after being forced to import following its 2009 drought. But falling global prices deter exports, even though the world's second biggest producer has surplus stocks.
Others: Corn, lentils, oilseeds and cotton are other important crops in Western and Central India that depend on the monsoon. India is a net importer of lentils and cooking oils and domestic output affects the size of its overseas purchases.
Average rainfall can allow the world's second biggest producer of cotton to sell the fibre overseas.
Economy and markets
Agriculture contributes about 15% of gross domestic product (GDP) in Asia's third-largest economy. Ample harvests can also ease inflation, which stands near 9%.
By lifting farm output, the monsoon boosts rural incomes, pushing up sales of everything from consumer goods to cars. Higher demand from rural consumers, who form two-thirds of a population of 1.2 billion, gives critical impetus to growth.
Higher farm income also boosts demand for gold in the world's biggest buyer, serving not only as a means of adornment but also investment, amid a sparse bank networks.
The rains fill reservoirs and swell groundwater, improving irrigation and power output. Higher rainfall can cut demand for the subsidised diesel that pumps water at irrigation wells and makes up about two-fifths of India's oil products demand.Graphics:
Monsoon rainfall in 2012
Farm output vs monsoon
Monsoon - forecast vs actual
Monsoon vs growth
India rainfall/droughts from 1910