Fishermen should not venture out into the sea on Monday as strong winds are likely.
An orange alert has been issued in three districts - Kozhikode, Kannur and Kasaragod - for June 15 and 16.
The rain will continue till Thursday, according to the India Meteorological Department.
Heavy rainfall is expected in Malappuram, Kozhikode, Kannur and Kasaragod districts.
The Met department said that Kerala is likely to get widespread showers from June 11.
According to the satellite imagery, there is an increase in cloudiness over the Kerala coast and adjoining the southeast Arabian Sea.
Monsoon's four-month sojourn in India accounts for 80 per cent of the country's rainfall. It is crucial for farming and replenishing the reservoirs and the groundwater table.
According to the India Meteorological Department, the monsoon is likely to be normal this year.
The inflow into the reservoirs, thanks to the tireless summer rains, is as high as 18.1 million units. In 2018, the inflow was less than 10 million units.
Releasing its second long range forecast for southwest monsoon 2021, IMD Director General Mrutunjay Mohapatra said June is likely to witness normal monsoon which is also the sowing season.