Heat doesn't sleep in Karnataka

For decades, heat governance in Karnataka has been built around daytime extremes: maximum temperatures, heatwave alerts, and midday breaks. But this framework is not sufficient. It is becoming a continuous, 24-hour stress.

Over the past two decades (2004-2024), the state has witnessed a steady rise in temperatures, with daytime highs increasing in the 0.13-0.7°C range and nighttime highs in the 0.17-0.72°C range across districts.

Karnataka now records nearly ten more warm nights each year than it did in 1990.

The growing frequency of warm nights where temperatures remain unusually high after sunset means that heat is no longer an episodic daytime hazard. What makes this crisis particularly dangerous is that it is invisible.

While extreme daytime heat draws attention, warmer nights quietly erode human health by preventing recovery from daytime exposure. Without cooler nights, the human body cannot reset, which compounds the risks: heat stress accumulates, sleep is disrupted, and vulnerability rises sharply among the elderly, outdoor workers, and those with limited or no access to cooling.

These impacts can intensify during ENSO (El Niño-Southern Oscillation) climatic events, when weakened monsoon circulation, reduced cloud cover, and prolonged dry conditions amplify both daytime and nighttime temperatures across southern India, thereby influencing the severity and persistence of heat exposure.

More concerning is the change in the Diurnal Temperature Range (DTR), which varies across districts between 15-25°C. A 1991-2024 analysis reveals a sharp shrinkage in DTR during the winter months (December-February) compared to summer (March-May), driven by rising nighttime temperatures in winter.

In the coastal belt, rising humidity and increasing heat stress ensure that nights remain stifling, even when temperatures are not peaking. As of 2026, in coastal districts like Dakshina Kannada and Udupi, temperatures routinely touch 38-40°C, but higher humidity of about 50% makes it feel closer to 49-55°C.

In the northern interior districts such as Kalaburagi and Vijayapura, prolonged high temperatures above 40°C are now followed by insufficient nighttime cooling, extending the physiological burden and adversely impacting public health, labour productivity, water availability, and heat stress conditions. 

Even the hilly regions like Kodagu and Chikkamagaluru – once considered natural refuges from heat – are no longer immune to heat stress. Temperatures are climbing above 30°C, with warmer nights threatening biodiversity and plantation crops like coffee and pepper.

Several protected landscapes, including Kudremukh National Park and Bandipur Tiger Reserve, are experiencing daytime temperatures that frequently cross 35-40°C and warmer nights with minimum temperatures rising 0.5-0.8°C over the past four decades. These changes are contributing to ecological stress and increasing risks to biodiversity and wildlife habitats.

Urban Karnataka presents an even more worrying picture. Over the past three decades, cities such as Mysuru have recorded a nearly 4°C increase in land surface temperature alongside declining (2%) vegetation cover, while Bengaluru has seen temperatures rise by as much as 15°C with a nearly 49% loss in green cover. Over the past decade, both Bengaluru and Mysuru have witnessed a sharp rise in warm nights, depriving residents of the cooling relief that nights once provided.

Shifting baselines

Heat is now an all-season challenge for Karnataka. The recent Karnataka Heat Action Plan 2026 marks an important step towards strengthening heatwave preparedness, response framework, and early warning systems. District heat action plans should include granular heat hazard projections and heat-risk assessments.

Expanding automatic weather station networks, mandating the collection and maintenance of heat-related data, and establishing local heat-risk monitoring systems is essential at sub-district levels.

Implementation of simple heat adaptation strategies at the sub-district level, like creating better airflow through ventilation corridors and considering community centres and schools as shelters, can be a good starting point.

Integrated policies across sectors, including climate, energy, urban planning, agriculture, and healthcare, must be designed around the reality of continuous heat exposure for building long-term resilience.

Climate change is not only intensifying extremes; it is altering baselines. Experts attribute this to a combination of global warming, climate variability such as ENSO events, urbanisation, land-use change, shrinking green cover, and rising humidity. The impacts are visible through rising heat-related health risks, declining labour productivity, increasing water stress, and growing cooling demand. Immediate, sub-district level action is critical. Given Karnataka’s diverse terrain and uneven heat exposure patterns, localised, district-specific interventions must be prioritised and implemented.

Sandhya is a senior advisor and Kala is a manager at Vasudha Foundation, a nonprofit think tank working to advance clean energy and climate solutions

(Disclaimer: The views expressed above are the author's own. They do not necessarily reflect the views of DH.)