As per historical data of the past 50 years, the long-period average (LPA) rainfall - between June and September - is 89cm. The IMD categorises rainfall in the 96 percent to 104 percent LPA range as normal while the rain immediately below that, it is considered below normal.
Monsoon is considered as "normal" if the average rainfall is between 96-104 per cent of the LPA.
On April 4, Skymet Weather said the Monsoon 2018 was likely to remain normal at 100 per cent (with an error margin of +/-5 per cent) of the long period average (LPA) of 887 mm for the four-month period from June to September. Monsoon rains is the lifeblood for India's farm-dependent 2 trillion dollar economy.
As per the IMD, there is 42 percent possibility of normal rainfall and 12 percent possibility of heavy rainfall - it means the country can witness some rainfall in the country. Operational forecasts for the southwest monsoon season rainfall are issued in two stages.
Despite "normal" forecast, the monsoon can be affected by the El Niño conditions.
IMD's forecast of 97% rainfall comes with a model error of (plus-minus) 5%.
Monsoon rains, the lifeline of the country's Dollars 2 trillion economy, are expected to be 97 per cent of a long-term average.
The onset of the monsoon in June kick-starts planting of rain-fed Kharif crops.
The rains after making a steady start in June and July, went for an extended break in August and also till early September which pulled down the total cumulative seasonal rainfall.
In good news for the country's agriculture sector and economy, the India Meteorological Department (IMD) has forecast a normal Monsoon this year. India had faced deficient rains during monsoon season in 2015 and 2014, making both these years drought years.