In Brief
- IMD data shows Assam's annual rainfall has decreased since the 1980s.
- Winter rainfall fell by 63%, while tropical warm nights rose sharply.
- Rainfall is now more concentrated in brief, intense downpours.
- Tree loss and urbanization are key drivers of rising temperatures and flooding.
A comprehensive analysis of 40 years (1985–2024) of gridded daily meteorological data from the India Meteorological Department reveals significant climate shifts in Assam. Annual rainfall has steadily declined from about 1,900 mm in 1985–2004 to roughly 1,400 mm after 2010, marking the driest phase in four decades.
Winter precipitation between December and February has decreased by 63%, dropping from 49 mm to 18 mm. Concurrently, tropical warm nights—temperatures above 25°C at night—have surged nearly tenfold, rising from 2.1 days per year to 20.8, culminating in a record 37 days in 2024.
Despite less total rainfall, the region faces increased risks of flooding due to the hyper-concentration of rainfall into intense, short-duration spells. The Gini coefficient measuring rainfall inequality rose from 0.779 to 0.809 across the analyzed periods, indicating more uneven distribution and longer dry spells within the monsoon.
Researchers attribute these changes to urban expansion, loss of tree canopy, and reduction in natural drainage systems, which diminish latent heat cooling and soil moisture. The loss of green infrastructure has transformed Assam’s microclimate, leading to warmer nights and vulnerable flood-prone urban landscapes.
Experts advocate for integrated approaches combining urban drainage improvements with citizen-led tree planting and restoration of wetlands to rebuild the region’s natural cooling and water absorption capacity.
