Why the city has warmth left over in the evening

Roads, roofs and walls store energy during the day and release it later. Paved surfaces also often lack cooling by evaporation. Especially on clear, calm nights, the city can stay warmer than its surroundings. This difference is the urban heat island.

What green spaces change

Trees provide shade, while plants and moist soil cool through evaporation. Their effect depends on vegetation, water availability, buildings and air exchange. An unshaded paved square can have different conditions from a green space.

A city has more than one temperature

Wind, shade, radiation and waste heat vary over short distances. The size of the differences depends on weather and time of day. Urban climate describes these recurring patterns; one hot afternoon alone is not a climate statistic.

In Hanover

Hannover was specifically measured

DWD investigated Hannover’s urban climate in 2017–2020, adding stations at sites including Weidendamm, Kronsberg and Linden-Süd. Mobile measurements complemented them. ÜSTRA trams and stations were studied too. Many passengers know a tram can feel warm; here that warmth was measured systematically.

The urban station at Weidendamm complements the long-running DWD station at Hannover-Langenhagen Airport, which represents a more rural setting. Airport climate normals therefore cannot simply be applied unchanged to a densely built courtyard.

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