The monsoon on Thursday simultaneously entered Kerala two days ahead of schedule and the Northeast six days ahead.

Favourable winds in the Bay of Bengal and the Arabian Sea drove the monsoon winds early.

A Met official in Calcutta ruled out the arrival of the monsoon in the city and the rest of south Bengal in “at least five days”.

The India Meteorological Department (IMD) said current weather conditions are favourable for the monsoon’s further advance into more parts of Lakshadweep and Kerala, and some parts of Karnataka, Tamil Nadu, remaining parts of the Northeast, north Bengal and Sikkim during the next two or three days.

“Southwest monsoon has set in over Kerala and advanced into most parts of northeast India, including entire Nagaland, Manipur, Mizoram, Arunachal Pradesh and most parts of Tripura, Meghalaya and Assam, today,” said a Thursday bulletin from the Met office.

“The northern limit of monsoon passed through... Coimbatore, Kanyakumari (both in Tamil Nadu), Agartala (Tripura) and Dhubri (Assam). Conditions are favourable for further advancement of southwest monsoon into some parts of sub-Himalayan West Bengal and Sikkim during next 2- 3 days.”

H.R. Biswas, the head of the weather section at the Regional Meteorological Centre, Calcutta, said: “There is no linear correlation between the monsoon’s early arrival in Kerala and its early onset in south Bengal.”

The normal date of the monsoon’s advance over Kerala is June 1 and the Northeast June 5, based on long-term weather data. The monsoon covers Bengal, eastern and central India by June 15 and reaches Delhi and northwestern India by June 30.

In north Bengal, the usual date of the arrival of the monsoon is around June 5 and in south Bengal, June 10.

Weather scientists have asserted in the past that the monsoon’s early arrival in Kerala or the Northeast has no correlation with its performance during the four-month season from June through September.

The Met office has predicted heavy rain in north Bengal.

“A trough runs from a cyclonic circulation over northwest Uttar Pradesh to west Bangladesh across southeast Uttar Pradesh, south Bihar and sub-Himalayan West Bengal and Sikkim at 0.9km above mean sea level. Due to the above system and strong moisture incursion over the region, heavy to very heavy rainfall activity is very likely over some districts of north Bengal,” the bulletin said.

Cooch Behar, Alipurduar, Jalpaiguri, Darjeeling, Kalimpong and North Dinajpur districts are likely to get drenched till at least June 3.

In south Bengal, localised and scattered thunderstorm activities are likely over the next few days. A Met official ruled out the possibility of uniform and widespread rain.

The IMD has also predicted a gradual abatement of the heat wave that has persisted across the northern and central Indian plains over the past 10 days. It said the maximum temperatures there will gradually fall by 2 to 4 degrees Celsius over the next five days.

Weather data over the past 24 hours shows “heavy to very heavy” rainfall in parts of Kerala, Mahe near Pondicherry, Assam, Lakshadweep, Arunachal Pradesh, Nagaland and Manipur. The heavy to very heavy rainfall is likely to continue in the Northeast during the next four to five days, the IMD said.