India and Pakistan are no strangers to heat. This time of year is the worst as the heat peaks before the monsoon brings cooler conditions from June.
But this year’s heat is something else. Strong and persistent heat began in mid-April. Daily maximum temperatures have reached 46°C in many places, with some areas going around 5-8°C above seasonal norms.
The unrelenting heat has brought a record DEMAND for electricity in India as people turn on air conditioners – and worsening drought conditions affecting more than a million square kilometers both countries.
When extreme heat combines with humidity, it can be deadly. Human bodies cannot cool easily under these conditions. Heat wave has affirmed at least 37 live in India and 10 in Pakistan. These numbers are likely to be a large underestimate, as are heat-related deaths systematically undercounted in India.
Why is it so hot?
It is usually a hot wait for the monsoon. But several factors can line up to make a bad season much worse.
One reason it has been so bad this year is the persistent high pressure weather systems. When these systems stay in place, they cause heat waves more likely suppressing cloud formation and reducing the chance of rain cooling. This year, strong high-pressure systems have lingered over parts of India and Pakistan, trapping hot air near the surface and allowing temperatures to soar for days.
With less rain, there is more heat at ground level and soils dry out. Drier soils make matters worse because less heat is used by evaporating moisture in the soil and more goes into warming the soil. High pressure systems can often sit around for many days, allowing extreme heat to build up.
It’s often worst in cities, as concrete and asphalt absorb heat during the day and slowly release it at night. This means cities stay hotter at night, increasing health risks for people without access to cooling.
Behind these immediate reasons lies the big one: climate change. As the world continues to heat up, heat waves get worse and worse. Ratings from World weather attribution suggest that the first major heat wave from 15-29 April 2026 was three times more likely and about 1°C hotter due to climate change.
At current global levels of global warming (~1.4°C), this means that the subcontinent faces similar events about once every five years. Currently, we are following straight 2.6°C of warming by 2100. At that level of heat, heat waves like this would hit every 2-3 years and be 2.2°C hotter.
The humidity makes the heat that much more deadly
The number on a thermometer is only part of the risk.
Many parts of India and Pakistan are very humid. When extreme sustained heat arrives, humidity acts to intensify health threat. Humidity levels are deteriorating in some parts of the country REGION.
This is because it is harder to cool down naturally in humid conditions. Human bodies use sweating as their primary method of cooling. When these beads of warm water evaporate from the skin, the heat is removed.
Humid air makes sweating a much less effective method of cooling. When the air already holds a lot of moisture, it takes longer for sweat to evaporate. The body can continue to heat up even when sweating.
That’s why scientists are getting more and more worried the deadly humidity – when heat and humidity combine to sicken or kill rapidly.
To die like this is deeply unpleasant. It starts with an increase in body temperature. People sweat more to try to get rid of the heat, but sweating doesn’t work well. If there is no rest, the body temperature can continue to rise above 40°C and heat stroke can occur, damaging the brain and other vital organs. This can be fatal without rapid cooling and emergency care.
To assess the combined risk of heat and humidity, scientists use measures such as wet bulb temp. This reflects how much cooling is possible through sweating.
The limit for human survival was previously thought to be a wet bulb temperature of 35°C. But new research shows that heat and humidity can be lethal in a variety of temperature and humidity combinations. For example, for elderly people outdoors, 35°C and 90% humidity is as deadly as 45°C and 30% humidity. These levels have already been reached during heat waves in South Asia the last few years. For example, even healthy 18-35 year olds risk dying at 40% humidity and 45°C temperature.
It is likely that some areas of the subcontinent reached those limits at some point during this intense period of heat. But we can’t say for sure, since most weather reports give air temperatures, not wet bulb temperatures.
A threat met unevenly
The dangers of heat and humidity are not met equally. Wealthier people can turn on the air conditioner and avoid going outside.
But the poorest people in informal settlements cannot escape the heat. Neither can construction workers, farmers, delivery riders and others who do hard physical work outside.
There is another danger. The body needs cooler temperatures at night to recover from intense heat. When the heat continues through the night, there is no relief.
While cities are hotter than surrounding areas, rural communities still are face threats from heat and humidity. This is because most work tends to be outside, health care is often far away and cooling is limited.
When can relief come?
When the monsoon arrives, it usually brings cooler conditions. Cloud cover and widespread precipitation help keep temperatures down during the day, although humidity often remains high. Monsoon usually comes in beginning of June in southern India and covers the entire country by mid-July. In Pakistanthe monsoon usually arrives later, usually starting in early July. The monsoon often lasts until September.
Relief cannot come too soon for the region.
Unfortunately, it will not be the last threat. But as climate change increases, extreme heat and moisture will hit these nations more often – and harder.
Oluwafemi E. Adeyeri is a researcher, ARC Center of Excellence for 21st Century Weather, Australian National University. Sarah Perkins-Kirkpatrick is Deputy Director, Engagement and Impact, ARC Center of Excellence for 21st Century Weather, Australian National University.
This article was reprinted from Conversation under a Creative Commons license. Read on original article.
