Wet Puja warnings intensified with Mahalaya rainfall as the Met office blamed it on 'well-marked low pressure' off the Sunderbans.
The weather office on Monday issued a warning for heavy rain in Calcutta and elsewhere in Gangetic Bengal over the next 48 hours and asked fishermen not to venture into the high seas.
With the low pressure intensifying and approaching the Bengal coast, the state government was alerted.
Alipore recorded 26.2 mm of rain till 2.30 pm on Monday, but Calcutta Municipal Corporation officials said Park Circus experienced 37 mm.
More than the intensity, it was the constancy that troubled Calcuttans and raised fears of a festival ruined by the rains. Acting deputy director-general of meteorology at Alipore K.K. Chakraborty admitted that rainfall caused by monsoon currents could not be ruled out during the Pujas next week.
'The monsoon generally bows out of Bengal between October 8 and October 15. But this year, it has started to withdraw late elsewhere in the country. We expect the trend in Calcutta, too. The Pujas, therefore, are being held in the thick of (retreating) monsoon. So, rains can always be expected,' said Chakraborty.
Monsoon matters could also be compounded by the formation of various kinds of low-pressure systems in the Bay of Bengal, ranging from depressions to cyclones. 'The cyclone season begins from October, and can bring rains and storms during the festival,' added Chakraborty.
The city suffered incessant rain from Mahalaya morning as the low pressure that lay over north-west Bay of Bengal, off the Orissa coast, on Sunday, crept upwards into land and intensified into a well-marked low pressure.
On Monday, it lay over coastal Gangetic Bengal off Sunderbans adjoining north-west Bay of Bengal and north Orissa.
Chakraborty, however, held out some hope for last-minute festive shoppers. The low pressure was unlikely to intensify as it had entered land, he said. 'Going by our calculations, it is expected to dissipate by October 6, and it is unlikely that any further low pressure will form in the same area in the next seven days.'
But if the low pressure doesn't get the city next week, the retreating monsoon or the cyclone system might.