The urban heat island — Geography, 11–13
Why built-up areas can be warmer than nearby countryside, especially after sunny days and at night.
Cities hold and make heat
An urban heat island is a built-up area that is warmer than nearby rural land. Dark roofs and roads absorb sunlight, concrete releases stored heat slowly, and tall buildings can block moving air. Cars, air conditioners and buildings add more heat, while fewer trees mean less shade and less cooling from evaporation.
Why study it?
People first noticed that temperature measurements differed between crowded streets and open countryside. The problem matters because extra heat can make sleep difficult, increase dehydration and raise energy demand during heatwaves. Geographers study the pattern so cities can cool the places where people are most exposed, rather than treating every street alike.
Comparing two places
At 10 p.m., a sensor records 27°C beside a city car park and 23°C in a nearby grassy park. Subtract the readings: 27 − 23 = 4°C, so the car park is 4°C warmer at that moment. To investigate fairly, repeat the measurements at the same time, in similar weather, and with sensors kept in the shade.
Not every city day is hotter
A reasonable mistake is to think every point in a city must be hotter than every point outside it. A shaded street beside a river may be cooler than sunny farmland, and wind or clouds can weaken the effect. The heat island is a pattern found by comparing many suitable measurements, not a rule about every single thermometer reading.
Cooling the city
Planners can reduce heat by planting trees, adding parks and ponds, using pale roofs and keeping air moving through streets. Trees cool in two ways: they provide shade and release water vapour from their leaves. Geographers help decide where these changes matter most, especially near schools, care homes and busy paved areas.
Keep exploring
Other languages
Loading MyLeoNes™…