India’s summers are no longer defined by rising temperatures alone. Increasing humidity is intensifying the impact of heatwaves, making it harder for the human body to cool itself. At the centre of this shift is the concept of wet-bulb temperature, a measure that combines heat and humidity to show how effectively the body can regulate temperature through sweating.
What wet-bulb temperature means
Wet-bulb temperature reflects the lowest temperature air can reach through evaporation. Unlike standard air temperature, it indicates how well sweat can evaporate and cool the body.
"When humidity is high, sweating becomes ineffective, making it extremely difficult for the body to regulate its temperature," NDTV quoted Dr Gaurav Batra, Neurosurgeon (Brain & Spine), Max Hospital, Vaishali, as saying.
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Per NDTV, research, including studies in Nature Communications and the Journal of Applied Physiology, highlights that a wet-bulb temperature above 35 degree Celsius is considered dangerous. Beyond this point, even healthy individuals may struggle to cope with prolonged exposure.
Why heatwaves are becoming riskier
India is facing a combination of rising temperatures and increasing humidity, particularly in coastal and urban areas. This raises wet-bulb levels and increases the risk of heat-related illnesses.
"When wet-bulb temperatures rise to dangerous levels, the risk of developing heat exhaustion and heatstroke increases rapidly," says Dr Batra.
Unlike dry heat, humid conditions prevent the body from releasing heat efficiently, leading to faster dehydration and internal overheating.
Impact on the brain
Extreme heat does not just affect physical comfort; it can also disrupt brain function. Per NDTV, findings reported in the journal Critical Care show that high temperatures can interfere with the brain’s normal processes.
Dr Batra notes that excessive heat may lead to blood-brain barrier disruption, brain cell dysfunction, and cerebral edema. Early symptoms can include confusion, headaches, and disorientation, while severe cases may involve seizures or coma.
Higher risk groups
Some individuals are more vulnerable than others. Those with a history of brain injury, intracranial bleeding, or recent neurosurgery face higher risks.
"In such cases, even a slight rise in body temperature can increase intracranial pressure, worsening the risk of secondary brain injury," explains Dr Batra.
Dehydration further reduces blood volume, affecting circulation to the brain and raising the risk of stroke and other complications.
Why awareness matters
As climate patterns shift, recognising early warning signs becomes crucial. Symptoms such as dizziness, fatigue, and confusion may indicate the body is struggling with heat stress.
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Understanding wet-bulb temperature helps explain why some heat conditions turn dangerous quickly. With rising humidity levels, the risk is no longer just about how hot it feels, but how the body responds under those conditions.
