Northeast India swings between heavier downpours and longer dry spells, signalling monsoon instability: 52-year study

Guwahati: A new national study tracking India’s weather from 1971 to 2022 finds that Northeast India is caught between two opposite extremes, heavier single-day downpours on one side and longer dry spells on the other.

The finding covers the region as a whole, which spans Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura, Arunachal Pradesh and Sikkim.

The study, titled ‘Evolution of Climate Extremes Over the Indian Subcontinent Using a Revised CEI’ and published in the peer-reviewed International Journal of Climatology by scientists at the India Meteorological Department (IMD) and the National Centre for Medium Range Weather Forecasting (NCMRWF), combined seven separate hazards, among them daytime heat, humid heat, heatwave severity and drought, into a single India Climate Extremes Index built on 52 years of IMD observations, with trends tested using the Mann-Kendall method.


The northeast is the only region where the study finds a clear, statistically significant rise in extreme one-day rainfall, which the authors link to a warming Bay of Bengal, greater atmospheric moisture and the region’s complex terrain. At the same time, dry spells and drought are becoming more frequent. Taken together, the authors read this as growing instability in the monsoon over the northeast, rather than a simple shift towards wetter or drier conditions.

“The northeast is the one region swinging between extremes, heavier single-day downpours on one side and longer dry spells on the other. That combination points to a more unstable monsoon, and it calls for both flood preparedness and drought planning,” said M. Rajeevan, co-author, Atria University, Bengaluru

“The northeast is the only part of the country where we see a clear rise in short, intense one-day rainfall, even as dry spells lengthen. It stands apart from the heat-and-drought story that dominates the rest of India,” added Thota Mohan, lead author, National Centre for Medium Range Weather Forecasting

The study names strengthening flood preparedness and rainfall-variability management as the priority for the northeast. It argues for a cross-sectoral response across agriculture, water management, health and infrastructure, and for finer-scale monitoring, since averages across the region can mask the localised extremes that drive flood and drought risk. The authors propose the index as an operational tool that agencies can run each year to track where stress is building.