The minimum temperature dropped to 17.6 degrees in Calcutta on Sunday, the first time the Celsius went under 18 degrees this season.

The Met office said northwesterly winds were dominant in the atmosphere. The minimum temperature predicted for Monday is 17 degrees.

The winds dragged the day temperature down as well. The maximum temperature recorded at the Alipore Met office was 26.9, more than two notches below normal.

A system in the distant seas is expected to become stronger by the next weekend but whether it has any bearing in south Bengal or not remains to be seen, the Met office said.

“Yesterday’s low-pressure area over east equatorial Indian Ocean and adjoining southeast Bay of Bengal has become a well-marked low-pressure area over southeast Bay of Bengal and adjoining east Equatorial Indian Ocean. It persisted over the same area over southeast Bay of Bengal and adjoining east Equatorial Indian Ocean at 8.30am today,” said a bulletin issued on Sunday by the IMD headquarters.

“It is likely to move west-northwestwards and intensify into a depression over central parts of south Bay of Bengal on November 25. Thereafter, it is likely to move northwestwards towards Tamil Nadu-Sri Lanka coasts during the subsequent two days.”

A Met official in Calcutta said: “The system is very far from the Bengal coast. If it extends till the Andhra Pradesh coast, some clouds can reach here and the coastal areas may get some rain around November 30.”

In Calcutta and much of south Bengal, the weather was pleasant on Sunday. At 12.1 degrees, Purulia was the coldest place in south Bengal.