What Is the Urban Heat Island Effect?
The urban heat island (UHI) effect describes how cities and towns tend to be noticeably warmer than surrounding rural areas, especially at night. This happens because pavement, rooftops, and buildings absorb and re-radiate more solar heat than natural land cover, while less vegetation means less cooling from shade and evapotranspiration.
How This Estimate Works
This calculator uses a simplified model that combines two well-documented UHI drivers: city size (larger, denser populations generally correlate with a stronger heat island, modeled here on a logarithmic scale since the effect grows more slowly at very large populations) and the balance between paved/built surface coverage and green space. The result is scaled to typical observed UHI intensities, which in real cities are commonly documented in the range of about 1 to 7°C (2 to 12°F) warmer than nearby rural areas, most pronounced at night in summer.
This is a simplified educational estimate, not a substitute for local meteorological monitoring or a professional urban climate study. Actual UHI intensity also depends on regional climate, building materials, water bodies, wind patterns, and time of day.