As temperatures rise, during the days and nights, Zurich tests bold ideas to beat the heat and protect city life from climate change.

Zürich

Zurich is trialling new methods to address rising urban temperatures, including the use of lighter, heat-reflective road surfaces that initial tests suggest could stay up to 5 degrees Celsius cooler than traditional materials. The city is also implementing a range of other measures, such as removing impermeable surfaces, planting trees, and greening building walls with fast-growing native plants to reduce heat radiation.

Experts note that the heat island effect is particularly strong in Zurich, with the city centre experiencing significantly more tropical nights than surrounding forests. While the city can quickly implement changes on public land, progress is slower on private property, prompting new regulations such as requiring permits to cut down large trees. Monitoring and further testing are ongoing as Zurich continues its efforts to adapt to a warming climate.

Tropical nights in Zurich: A city trying to beat the heat

Laying this road surface works just like any other, but the team from Zurich's civil engineering department may be feeling the pressure today. This residential street on the edge of the city is paving the way for the future. New road-building methods are being tested. After grinding, the surface turns lighter. In summer, it could stay cooler by up to 5 degrees Celsius. You see here the lightest result we can get. The difference is huge. Are you sure it'll heat up less than a darker surface? Initial tests point that way. We still need to take a closer look at the test sections. But we're confident it's a good choice. The climate is changing. Hot days are becoming more frequent. And so are tropical nights, as they're known, when temperatures stay above 20 degrees Celsius. Experts are studying Zurich's urban climate. Their data shows the heat island effect is especially strong here. In 2023, only a few tropical nights were recorded in the forests outside the city. But in the densely built-up city centre, shown in red, there were more than 25 tropical nights in some areas. If the city can't cool down at night, we start the next hot day already at a high temperature. After five hot days, we see lots of tropical nights, or tropical nights in lots of areas. Based on these findings, the city has developed a whole catalogue of measures. New buildings are designed to let cool air flow into the city centre. Impermeable surfaces are being removed, and trees are being planted. Walls are also being greened to reduce heat radiation. In Zurich-Altstetten, nature consultant Michael Hagenauer has chosen native plants. Sensors measure how much they cool a wall. The advantage of climbing plants is that they grow fast. While a tree might take decades to reach full size, vertical greening speeds things up. Some plants reach several metres in just two to three years and create a full green cover. Michael Wagner is a professor of urban design. He says that while many heat reduction measures are underway, Switzerland still isn't making the most of its potential. First people need to understand how urgent these measures are. Then we need the political will to act. On public land, things can move quickly. The city has the authority to implement these measures. But on private property, it takes longer. In fact, Zurich's tree population has recently declined. That's why a new and controversial rule now requires a permit to cut down large trees, even in private gardens. Heat-reflective road surfaces, on the other hand, are likely to face less resistance. But before they can be rolled out across the city, this new stretch has to pass all the tests. Heat sensors will be mounted on streetlights and used for monitoring. It's just one of many efforts to get the heat under control. But cooling down the entire city, that's a long road ahead.

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