The summer monsoon is expected to reach Kerala on June 5, the India Meteorological Department said on Friday, predicting a slight delay from the usual onset date of June 1.

A low pressure area over southeast Bay of Bengal likely to intensify into a cyclone by Saturday evening is among factors contributing to this slight delay of three or four days, a senior IMD scientist said.

The onset forecast comes with an inherent error margin of four days, implying the onset could take place any day between June 1 and June 9.

For its onset date forecast, the IMD uses six weather parameters, including minimum temperatures in northwest India, wind conditions over the east equatorial and southeast Indian Ocean and atmospheric conditions over the south China sea and southwest Pacific.

“Right now, we also have a low pressure area over southeast Bay of Bengal that is expected to evolve into a cyclone by Saturday evening — winds and moisture will be pooled into this region,” Mrutyunjaya Mohapatra, IMD director general told The Telegraph.

“This is a temporary disturbance affecting circulation in the region,” he said.

Along with the cyclone, atmospheric conditions are likely to become favourable for the monsoon to advance into the Andaman Sea and across the Andaman and Nicobar islands and parts of southeast Bay of Bengal over the next 48 hours, the IMD said.

Weather scientists say years of observations have revealed no correlation between the date of onset and the subsequent performance of rainfall during the four-month monsoon season. The IMD, in its first long-range forecast for the 2020 monsoon last month, predicted that rainfall from June through September is likely to be 100 per cent normal, assigning probabilities of 41 per cent for normal and 21 per cent for above normal rainfall.