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Night Temperature Increase: Rising night temperatures are no longer just a source of discomfort but have become a potentially life-threatening health risk. This silent killer is having a dangerous impact on our sleep and health.

What effect do hot nights have on the body?

The mercury is soaring past 45 degrees Celsius during the day, and even higher at night, it's rising by 5 degrees Celsius. This isn't just a weather report, but the horrifying reality of this year, robbing millions of Indians of their sleep and health. In the last week of April 2026, more than 17 cities across the country recorded minimum night temperatures 5 degrees Celsius above normal. This increase isn't just a statistic; it's proving to be a "silent killer" for the human body. Let's understand what this "night heat" is, how it's damaging the body, and why the situation is set to worsen in the coming days...

What does it mean if the night temperature rises by 5 degrees?

When we talk about a '5-degree rise in night temperature,' it means that the mercury is staying much higher than normal after sunset. For example, in Delhi, night temperatures during April 2026 consistently remained above the 2020-2025 average and the 1991-2020 normal. On April 29, it rose to 28.5 degrees Celsius. Meanwhile, in Hyderabad, the minimum night temperature remained stable at 28.8 degrees Celsius, 2 degrees above normal.

These are called "warm nights" or "hot nights." Scientists define this as a condition when nighttime temperatures are so high that the body doesn't have a chance to recover from the day's heat. This condition is no longer limited to May and June, but is now visible in April as well.

What happens to the body when the nights are hot?

In fact, the human body is designed as a natural cooling system. After the intense heat of the day, the cool night temperatures restore the body's core temperature to normal, allowing our body parts to rest and recover. However, when nighttime temperatures remain between 28-30 degrees Celsius, this natural process is completely disrupted. One study even suggests that if nighttime temperatures exceed 30 degrees Celsius, mortality rates can increase by 265%.

Understand its effect on the body like this:

• Direct injury to the heart and brain: Consistently hot nights multiply the risk of heart disease and stroke. Reports suggest that the risk of death on hot nights is 50% higher than on normal nights.
• Attack of diseases: Hot nights not only cause heat stroke but also seriously increase non-communicable diseases like diabetes and hypertension.
• Deterioration of mental health: Poor sleep due to heat weakens the immune system, disrupts concentration, increases fatigue, and has a very negative impact on mental health.

Even AC and coolers are failing, why can't I sleep?

At the root of all this is sleep deprivation. Cooling down is crucial for our bodies to sleep. A study in Chennai found that temperatures inside middle- and lower-middle-class homes remained above 32 degrees Celsius at night, reaching 35 degrees Celsius in some cases. Walls and ceilings absorb daytime heat and radiate it at night, rendering fans and coolers ineffective. A controlled study also found that rising nighttime temperatures increase core body temperature during sleep, leading to shallow and incomplete sleep.

Why are cities burning like a pan?

Senior environmentalist Dr. Professor Subhash C. Pandey believes that this problem is even more severe in cities due to the "urban heat island effect." Concrete, roads, bricks, and metal in cities absorb heat during the day and release it at night. Lack of greenery, depletion of water bodies, and the multitude of high-rise buildings further trap this heat. 93% of districts fall into the very high or very high heat risk category. A major reason for this is the formation of urban heat islands.

Will the situation worsen further in the coming days?

The heat wave isn't going to stop here. According to a climate assessment, by the end of this century, the hottest daytime temperature in India could rise by 4.7 degrees Celsius, while the coldest nighttime temperature could jump by 5.5 degrees Celsius. This means that nights will warm faster than days. This can be gauged from the fact that nighttime temperatures are consistently rising to dangerous levels in 83% of the world's major cities.

This picture is scary, but this danger can be reduced by taking some simple measures:

• Stay hydrated: Drink plenty of water and electrolyte-rich liquids not only during the day but also in the evening and at night.
• Try to keep your home cool: Draw curtains on windows during the day to prevent heat from entering. Create cross-ventilation at night. If possible, use "cool roof" technology on your rooftops.
• Change your sleeping habits: Wear light cotton clothing. Use cotton sheets. Avoid heavy meals before bed.
• Special care for vulnerable individuals: The elderly, children, pregnant women, and those with pre-existing medical conditions are most vulnerable to hot nights. Therefore, the health of these family members requires special attention.
• Administrative Initiatives: Governments and urban planning agencies must include monitoring and mitigating nighttime temperatures in their heat action plans. Currently, most plans focus solely on daytime heat. Increasing greenery in cities, reviving ponds, and creating ventilation corridors are crucial steps for the future.

After all, how big is this crisis?

Dr. Subhash C. Pandey says, "This is no small problem. 57% of the country has fallen into the high heat risk zone, where 76% of the country's population lives. Between 2012 and 2022, more than 70% of districts experienced five or more additional hot nights each summer . This is a nationwide health crisis that is gradually worsening."

Rising nighttime temperatures are no longer just a source of discomfort but a potentially life-threatening health risk. When the body doesn't get any relief at night, it's unable to prepare for the next day's heat, and this cycle continues to tear us apart, a little at a time, each day. For now, the best defense lies in understanding the impact this silent killer is having on our sleep and health, and taking preventative measures.