Uneven Monsoon Distribution Hides Severe Regional Rain Deficits In India

The monsoon is not over yet. But rainfall this season has not been evenly spread across India. The India Meteorological Department (IMD) had forecast below-normal rainfall for the June-September monsoon season, with the season expected to remain below the normal level.

The question now is whether the rain that has fallen has been spread evenly across the country.

The answer is no. Some days have seen little or no rain, followed by spells of heavy rain that have caused waterlogging and flooding. Delhi-NCR and Gurugram are examples of this pattern. In Gurugram, more than 60 mm of rain was recorded in a single day, leading to waterlogging in several areas.

The rainfall recorded in Delhi so far this monsoon also shows why the seasonal total does not tell the whole story.

Uneven Rainfall

From June to August, Delhi's rainfall departure stood at 14 per cent, which falls in IMD's normal category. But the daily rainfall figures show that the rain has not been evenly distributed.

Delhi received about 32.9 mm in June, 261.5 mm in July and 354.1 mm in August. Within these months, several days recorded little or no rain, while a few days saw sharp increases.

On July 9, Delhi received 72.6 mm of rain. On August 8, rainfall reached 98.7 mm, while August 25 recorded 99.1 mm. On several other days, rainfall was below 5 mm, or there was no measurable rainfall.

So, even though Delhi's cumulative rainfall was in the normal range, the rain did not arrive at a steady pace. A few heavy spells contributed a significant share of the rainfall received during the season.

India's Rainfall

The picture across India is also mixed. From June to August, India received 603.7 mm of rainfall against the normal 700.7 mm, leaving the country with a 13.8 per cent deficit, according to IMD. East and Northeast India had the largest deficit. Northwest India was 11 per cent below normal, while Central India was 2 per cent below normal.

The state-wise figures show similar differences. Only three States and Union Territories in the data recorded excess rainfall: Ladakh (195 per cent), Dadra and Nagar Haveli and Daman & Diu (45 per cent) and Odisha (26 per cent).

Delhi stood at 14 per cent, while several states remained in deficit.

Bihar was at -42 per cent, Manipur at -43 per cent, Arunachal Pradesh at -41 per cent and Andhra Pradesh at -42 per cent.

The pattern may continue into September. IMD's extended-range outlook for September 3 to 9 indicates below-normal rainfall over most parts of India. East and east-central India are expected to receive normal to above-normal rainfall, while parts of the Northeast, West Bengal, Odisha, Jharkhand and Bihar could receive heavy to very heavy rain at isolated places.