The City That Never Cools Down

Pune, summer evening. The sky still holding the heat of the day.

The moment I know summer has truly arrived is not the afternoon sun. It’s the evening.

I get home after a long commute, already hot, already tired, and the first thing I feel is the floor. Warm. Not warm like it absorbed a little sun through the window. Warm like a furnace that was just switched off, still radiating everything it stored through the day.

I open the windows, turn the fan to full. It doesn’t matter. The air coming in is barely cooler than the air inside.

Cooking dinner in this doesn’t feel like a chore. It feels like punishment.

And if you’ve felt this too, you’ve probably noticed something else:

It doesn’t really cool down at night anymore.

Here is something most heat coverage misses: the number that should worry us most is the overnight low.

We tend to measure heat by the afternoon peak, the 42°C that makes headlines. But the human body isn’t built to endure heat continuously. It’s built to take the hit during the day and recover at night.

Core temperature drops. Heart rate slows. The brain clears out metabolic waste (harmful amyloid-beta and tau proteins) from brain tissue, built up during the day.

Sleep is, quite literally, when the body repairs itself.

How the body is supposed to recover. And how it struggles when nights stay hot | Image: AI Generated

And this process depends on one thing: cooling.

As the body prepares for sleep, it sheds heat. That drop in core temperature is what helps us fall asleep. When the night air stays hot, that mechanism struggles. Sleep becomes shallow, broken, insufficient.

Do this for a few days during a heatwave, and the effects start stacking up. Exhaustion, cardiovascular stress, reduced focus, and slower recovery.

What we are experiencing has a name. Scientists call it the Urban Heat Island (UHI) effect, where cities stay warmer than the surrounding rural areas.

Think of UHI like a blanket that the city wraps around itself, storing heat in concrete, asphalt, and dense construction.

During the day, both cities and rural areas heat up.

At night, rural areas begin to cool more efficiently.

How cities hold on to heat after sunset | Image: AI Generated

There’s vegetation, moisture in the soil, and open space that allows heat to escape upward. Plants release water vapour into the air through transpiration, a bit like slow, continuous sweating. That moisture helps cool the surrounding air, making nights feel noticeably lighter.

Cities don’t have as much of that built-in cooling.

Instead, the heat is experienced in a very specific place. The space between buildings, along streets, inside neighborhoods.

This space has a name: the urban canopy layer.

It’s the dome like layer of air from the ground up to roughly the height of buildings. This is the space where we actually live, walk, and feel the heat.

And this is where the difference between rural and urban really begins to matter. Because inside this layer, the structure of the city starts to control how heat behaves.

Buildings sit closer together. Streets are narrower. The sky is partially blocked.

Wind doesn’t move as freely.

Heat doesn’t escape as easily.

So even after sunset, the air around us, within this layer, stays warmer for longer.

That’s why the Urban Heat Island effect feels strongest at night.

Not just because the city stored heat during the day, but because the space we live in doesn’t let it go easily.

The city, it turns out, has a long memory for heat.

Research on Indian cities shows nighttime temperature differences of 1 to 5°C compared to nearby rural areas. And that night part is what we don’t talk about enough.

Because this isn’t just about discomfort.

Think about what this means for someone who has already spent the entire day in the heat. Commuting, working outdoors, moving through the city.

A construction worker.

A delivery rider.

A street vendor.

If the night doesn’t cool down, the body doesn’t reset.

And the thing is, this heat isn’t felt the same way by everyone.

For some, there is a way out. A cooler room, an air conditioner, a properly ventilated room. For others, the heat doesn’t switch off. It follows them from the street into their homes, and stays through the night.

In that sense, heat is also an injustice. Not loud or visible, but uneven in who it exhausts, and who gets to recover.

In a country where a large share of the workforce depends on heat-exposed work, that missing recovery is not a small thing. It builds quietly, day after day.

This is a hidden tax of living in a warming city.

So, the question worth asking is: do we just accept this?

Maybe not. But the answer isn’t as straightforward as it sounds.

Because cities don’t just heat up because it’s summer.

They heat up because of how they’re built, and how they cool.

In Medellín, adding shaded corridors and green stretches brought temperatures down across parts of the city by 2°C.

But what stands out isn’t just the cooling. It’s how intentional it was.

The plants weren’t chosen at random. The technical team studied 75 endemic plant species that could actually survive the local heat, support biodiversity, and meaningfully cool the city, and built around that.

In Singapore, greenery isn’t something added later. It’s built into how the city functions.

Different approaches. Same underlying idea.

Make it easier for heat to leave.

And also understand what you’re adding back in. Because it’s not just about planting more.

It’s about planting right.

And just as importantly, holding on to what already exists.

A fully grown tree is already doing quiet, invisible work. Cooling, shading, holding moisture.

A new one takes time to get there.

And in a city that’s already heating up, that gap is something you can feel.

India has made a start — 23 states now have Heat Action Plans, covering different cities. Early warning systems, healthcare preparedness, community outreach. The framework exists. But a plan that works in Ahmedabad doesn't automatically work in Bhubaneswar or Nagpur. Local context, local species, local communication — the details matter as much as the intention.

And for Indian cities, this matters more than most. We are urbanizing fast, and the decisions being made right now, what gets built, what gets paved, what gets cut down — will determine what our nights feel like a decade from now.

The window to get this right is not closed. But it is narrowing.

City after midnight. Still warm. Still holding on. 

Right now, as I’m writing this, it’s still the afternoon. The fan continues to stay on the full speed, and I can already feel the heat settling in. And I keep thinking about what tonight is going to feel like.

How much of this heat is going to stay?

How much of it will follow into the night?

I wonder how much of today’s heat the city will still be holding on to.

Update: I got my answer. Temperatures in Pune crossed 41.8°C on 26th April 2026 — the day I wrote this article.

References:

Henry Ford Health Staff. (2026, March 16). How your brain cleans itself during sleep. Henry Ford Health. https://www.henryford.com/blog/2026/03/how-your-brain-cleans-itself-during-sleep

Kumar, R., Mishra, V., Buzan, J., Kumar, R., Shindell, D., & Huber, M. (2017). Dominant control of agriculture and irrigation on urban heat island in India. Scientific Reports, 7(1), 14054. https://doi.org/10.1038/s41598-017-14213-2

Cleveland Clinic. (n.d.). Glymphatic system: What it is, function & how it works. https://my.clevelandclinic.org/health/body/glymphatic-system

Mongabay. (2025, August). How urban greening is helping Singapore bounce back from widespread forest loss. https://news.mongabay.com/short-article/2025/08/how-urban-greening-is-helping-singapore-bounce-back-from-widespread-forest-loss/

Press Information Bureau. (n.d.). Heat action plans in India. Government of India. https://www.pib.gov.in/PressReleasePage.aspx?PRID=2134746&reg=3&lang=2

Reasons to be Cheerful. (n.d.). How a Colombian city cooled dramatically in just three years. https://reasonstobecheerful.world/green-corridors-medellin-colombia-urban-heat/

UrbanShift. (n.d.). How cities are beating the (urban) heat. https://www.shiftcities.org/post/how-cities-are-beating-urban-heat