Greater Chennai · 30 m Landsat · 2016–2026

Where Chennai Bakes

Some streets in this city run four degrees hotter than others on the same morning. Not because the weather is different — because of what the ground is made of, and how far it sits from the sea. Search your street, your neighbourhood or your ward.

—clear mornings measured
—places you can look up
110 mmap resolution
—hottest to coolest

The heat map

Colour shows how much hotter or cooler each patch of ground is than the half-kilometre around it, on the same morning. Not hotter than the city — hotter than its own neighbourhood, which is the part a roof or a row of trees could change. Roads are drawn on top so you can find your way around.

5 km
−4°C cooler−2 same as around it+2+4°C hotter
—

The ranking

Hottest first, for the view selected above. Pick any row to place it on the map.

Heat by area

The same data, summarised instead of pixel by pixel. Choose what to divide the city into, and which morning to measure. Averages compress the range, so this map has its own scale — the numbers under it say what the colours mean.

Divide by
Measure

Fifty places, and what would actually help

The maps above say where the ground is hot. This says why, place by place — what each one is made of, and which measures have evidence behind them there. The figure is against the city average rather than the local surroundings, because that is the comparison a city-wide shortlist has to be made on.

Each dot is one of the fifty places, sized and coloured by how far it sits from the city average.

What actually makes a place hot

Every type of land, measured at its own distance from the sea, on the same local scale as the map above. Reading down a column compares land types in the same setting; reading across a row shows what the coast does to one type of land. Both matter, and the coast matters more than most people expect.

coolerhotter

What this map is not

Ground, not air
The satellite measures how hot surfaces are — roads, roofs, bare earth. Air temperature differences between places are smaller, typically two to four times smaller than what you see here. A +3°C patch is not three degrees hotter to stand in; it is ground that radiates noticeably more heat at you.
Morning only
Landsat passes over Chennai at about 10:30 in the morning. Nothing here describes the 3 pm peak, and nothing describes the night — which is when heat does the most harm to health.
Local, and relative
Every number compares a patch of ground with the roughly half-kilometre circle around it on the same morning — not with the city, and not with a thermometer reading. On a 40°C day the whole map is hot; this shows where the ground is hotter than its own neighbours.
Clear days, March to June
Cloud blocks thermal imaging, so only clear pre-monsoon mornings are included — Chennai's hottest season, and the one worth mapping, but not the whole year.
Ward names are ours
Greater Chennai Corporation numbers its wards but the boundary file carries no names, so the name beside each number is the largest named locality inside that ward, taken from OpenStreetMap. It is a signpost, not the official name, and a ward usually covers several localities.
A street is a line
A road's figure is the average along its whole length, so a long road that crosses very different areas gets an average that describes none of them. Wards average over their whole area, which hides the hot patches inside them.