High Humidity Poses Major Heat Risks in Assam Despite Missing Official Thresholds

Assam continues to face severe heat stress even though temperatures in the state rarely meet India's conventional heatwave criteria. Under India Meteorological Department rules, a heatwave is declared only when maximum air temperatures hit 40°C in plains and depart from normal by 4.5°C to 6.4°C for two days, or reach 45°C outright. However, several stations across Assam have recorded maximum temperatures above 37°C and sometimes 40°C in recent years. In September 2023, Guwahati recorded 38.2°C and Silchar reached 39.4°C. On May 25, 2024, Guwahati hit 40.1°C, and later that year broke its all-time September temperature record with 39.3°C. In July, maximum temperatures in Guwahati, Dibrugarh, Tezpur and Dhubri were 4-5°C above normal, prompting a rare yellow alert from the IMD.

Urban Heat and Climate Trends

Urban heat assessments by the Directorate of Town and Country Planning between 2020 and 2025 show that land-use change, shrinking water bodies, loss of greenery and unplanned development are altering thermal landscapes in Guwahati, Dibrugarh and Silchar. The Assam State Action Plan on Climate Change 2.0 records a consistent warming trend between 1990 and 2019, with annual average maximum temperatures rising by 0.049°C per year and minimum temperatures rising by 0.013°C per year across all districts. Because the IMD had not declared heatwaves in Assam, the state previously did not consider heat a major risk and lacks a Heat Action Plan, unlike more than 250 cities and districts in 23 other heat-prone states. Recent district advisories have instead relied on school closures, revised timings, and outdoor restrictions.

The Humidity Factor

The primary driver of severe heat discomfort in Assam is high relative humidity, which is not currently part of the IMD heatwave criteria. During pre-monsoon and monsoon months, relative humidity in the state ranges between 75% and 95%, trapping body heat and slowing sweat evaporation. On May 25, 2024, when Guwahati reached 40.1°C, the apparent or feels-like temperature peaked at around 52°C. On September 23, 2024, apparent temperatures reached 53°C, and on July 4, 2026, a 36°C air temperature pushed feels-like readings to 52°C. Environmental scientist Partha Jyoti Das notes that standard dry-bulb temperatures rarely cross 40°C in Assam, but a temperature of 35°C paired with over 80% humidity can create a wet-bulb temperature of 31-32°C, generating severe physiological stress. An October 2026 IMD report also found that calculated Heat Index values exceeded 40°C from May to October during 2022-2024, peaking at 55.5°C in September and falling into the 'Extreme Danger' category for heatstroke risk.

Impact on Children

High heat exposure heavily impacts vulnerable populations such as children. A 2026 study cited in the report found that human-induced climate change has increased exposure to heat-stress days globally, with up to 560 million children under 10 experiencing at least one additional month of heat stress every year. Madhulika Jonathan, UNICEF Chief of Field Office for Assam and Northeast States, stated that children are physiologically less able to regulate body temperature and face risks across health, nutrition, water access, and school attendance on top of the state's recurring floods.

Context

While traditional weather reporting focuses primarily on dry-air temperature readings, humid tropical regions like Assam demonstrate that moisture in the air can make moderate thermometer readings feel dangerously hot. Climate scientists and public health officials are increasingly looking at wet-bulb temperatures and heat indices rather than air temperature alone to understand how extreme weather impacts human health and daily survival.