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Uttar Pradesh has taken a pioneering step by becoming the first Indian state to establish specific heatwave thresholds for all 75 of its districts. This will help the administration of each district can create its independent early warning system.
The decision will empower the district disaster management authorities to declare heatwaves based on these specific thresholds and activate heatwave action plans without waiting for broader declarations from the India Meteorological Department (IMD).
The initiative introduces a three-tier alert system — yellow, orange and red — designed to protect public health, optimise agricultural practices and improve urban planning in response to rising temperatures. By issuing district-specific warnings, the state aims to prevent heat-related illnesses and facilitate the timely implementation of medical support based on local temperature conditions.
Recognising that temperature variations exist across different regions, Uttar Pradesh’s new heat thresholds address the limitations of current standards set by IMD. The central meteorological agency defines a heatwave based on a blanket temperature of 40 degrees Celsius for plains, which may not be universally applicable.
The calculated heat thresholds for Uttar Pradesh reveal a significant range, with yellow alert temperatures spanning from 36.47-40.58°C, orange alerts ranging from 39.08-43.30°C and red alerts from 41.48-45.34°C across various districts. This diverse set of thresholds — from moderate to extreme — necessitates robust heatwave mitigation and adaptation strategies tailored to the specific needs of each district.
The State Disaster Management Authority (SDMA) conducted an extensive study that analysed temperature patterns from 1982 to 2023, resulting in the development of this three-tier alert system. By establishing these thresholds, Uttar Pradesh aims to reduce its reliance on IMD guidelines, which define a heatwave as temperatures exceeding normal levels by 4.5-6.4°C or exceeding 40°C in plains, 37°C in coastal areas and 30°C in hill regions.
Kashif Imdad, member of the state advisory committee of SDMA and study’s lead expert, highlighted that heat thresholds are specific temperature metrics used to issue alerts for each district.
To determine these thresholds, the expert panel incorporated IMD’s methodology of analysing deviations from normal temperatures, in consultation with the World Meteorological Organization (WMO) and the World Health Organization (WHO). They established the 50th percentile of maximum temperature for each district as the usual temperature, utilising the 80th, 88th and 95th percentiles to calculate yellow, orange and red alert temperatures, respectively.
The WMO-WHO guidelines suggest using percentile-based thresholds to trigger early warning systems, particularly when mortality or morbidity data is unavailable. By applying the 80th, 88th and 95th percentiles, Uttar Pradesh ensures a well-phased approach to understanding heat events and preparing to respond to extreme heat impacts effectively. This evidence-based heatwave early warning system is unique to each district and allows local authorities to measure threshold temperatures accurately.
Certain regions, such as the Bundelkhand districts, have been identified as particularly vulnerable to high temperatures, necessitating immediate red alerts. Districts like Banda, Jalaun and Mahoba have recorded some of the highest red alert temperatures, while others, including Prayagraj, Kanpur and Hamirpur have reported significant impact to daily life and agricultural productivity due to extreme heat.
As extreme heat events become more common, the study proposes the introduction of a ‘Century Alert’, which would correspond to the 99th percentile of temperature data, alerting the public and authorities to exceptionally severe heat waves. This new alert category would indicate temperatures that occur approximately 2.05 days each year on average.
Heatwaves have been shown to increase mortality rates, particularly among vulnerable populations. Uttar Pradesh, which accounted for 19.3 per cent of India’s total workforce in 2022, has suffered significant economic losses due to heatwaves.
Between 2001 and 2020, the International Labour Organization estimated an annual average loss of 50.271 billion labour hours, translating to around 1.38 million full-time jobs annually. The overall economic impact of these heatwaves reached around Rs 88,780 crore, equivalent to roughly $1.1 billion.
Understanding the complexities of heatwave occurrences will enable policymakers, researchers, and communities to develop targeted strategies that mitigate vulnerabilities and bolster resilience against the impacts of extreme heat. This initiative not only sets a precedent for other states in India but also serves as a crucial step toward safeguarding public health and ensuring sustainable agricultural practices in a changing climate.