The southwest monsoon that contributes 70 per cent of the annual rainfall, hit India’s mainland on Thursday, two days ahead of its normal schedule. The monsoon also advanced into most parts of northeast India six days before the normal date as well as some parts of Tamil Nadu.

India Meteorological Department (IMD) had predicted monsoon onset over Kerala on May 31. The monsoon had advanced into the Andaman and Nicobar Islands on May 19 as predicted by IMD.

“Southwest monsoon has set in over Kerala and Mahe and advanced into most parts of northeast India including entire Nagaland, Manipur, Mizoram, Arunachal Pradesh and most parts of Tripura, Meghalaya and Assam on May 30, 2024,” IMD said in a statement. It has also advanced into most parts of Lakshadweep area and some parts of south Tamil Nadu including Coimbatore and Kanyakumari, the weather bureau said.

Normally, southwest monsoon sets in over Kerala on June 1 and it advances over most part of northeast India by June 5.

Kerala and some States in the northeast region have been experiencing heavy to very heavy rainfall in the past few days. A team of the National Disaster Relief Force reached the northeast region on Wednesday as there were reports of deaths due to heavy rains.

“A cyclonic circulation lies over northeast Assam and neighbourhood in lower and middle tropospheric levels. Under its influence fairly widespread to widespread light to moderate rainfall accompanied with thunderstorm, lightning and gusty winds (30-40 kmph) are likely to be experienced over Arunachal Pradesh, Assam and Meghalaya, Nagaland, Manipur, Mizoram and Tripura and Sub-Himalayan West Bengal and Sikkim during next seven days,” IMD said in a bulletin.

Also, isolated heavy/very heavy rainfall is very likely over Arunachal Pradesh, Assam and Meghalaya, Sub-Himalayan West Bengal and Sikkim during the next five days, and isolated heavy rainfall over Nagaland, Manipur, Mizoram and Tripura on Thursday, IMD said.

The weather bureau on May 28 released its second monsoon forecast and said that rainfall is likely to be above normal at 106 per cent of the long-period average (LPA) of 87 cm this year. Rainfall in June will be normal, which is 92-108 per cent of the long period average (LPA) of 16.69 cm, IMD’s director general M Mohapatra had said.

While central and south peninsular India will receive above-normal rainfall (106 per cent of LPA), the northwestern part, a key region for the production of kharif crops, will likely receive 108 per cent of the LPA rainfall, according to IMD.

However, the IMD said the northeastern part of the country will receive below-normal rainfall at less than 94 per cent of the LPA. Mohapatra said the monsoon Core Zone, consisting of most of the country’s rainfed agriculture areas, is likely above normal (more than 106 per cent of LPA). This zone comprises parts of Rajasthan, Gujarat, Maharashtra, Madhya Pradesh, Chhattisgarh, Odisha, parts of Jharkhand, and Telangana.

The rainfall in the pre-monsoon season from March 1 until May 29 was 4 per cent below normal at 12.08 cm, against 12.58 cm considered normal for this period. On May 29 alone, the pan India rainfall was 54 per cent above average as Kerala reported 3.13 cm rainfall against 1.34 normal for the day while Arunachal Pradesh reported 3.46 cm rainfall (against the day’s normal of 1.26 cm), Assam and Meghalaya together had 4.55 cm (1.22 cm normal), Nagaland, Manipur, Mizoram and Tripura together had 3.96 cm (0.98 cm).