Sketch of an urban heat island profile.

UHI= T(urban)-T(rural)

The temperature of the urban area is higher than that of the rural area by 1.8–5.4°F (1–3°C). On the left side, temperature level is shown. The red curve shows the difference of temperature in rural and urban area at the given time. This change in temperature is caused by the different earth surface material in urban area, less vegetation, and blockage of wind flow.