St Pölten turns to mist and trees for summer cooling

St Pölten is using a misting system, water features and a watered artwork to cool public spaces on hot days, ORF reports. Residents welcomed the measures, although the amount of water used has prompted debate.

Under a clear sky and temperatures of 30 degrees, the largely empty, car-free cathedral square was crossed quickly by most passers-by. Many walked through the misting system, which sprays water into the air through 360 small nozzles in the ground.

As the water evaporates, it removes energy from the surroundings and lowers temperatures nearby. Passers-by also described the moisture on their skin as pleasant.

The system operates daily from 10 a.m. to 8 p.m., except on market days, when the mist would disturb stallholders. It runs when temperatures exceed 22 degrees and humidity is below 70 percent. After 10 minutes of operation, it pauses for 10 minutes. Its maximum water consumption is 30 cubic metres per week. By comparison, watering a football pitch once requires between 70 and 140 cubic metres of water.

Some passers-by have questioned why more trees were not planted on the cathedral square. The city says this was not possible because of heritage protection: the remains of a Roman palace and a cemetery lie beneath the square. Several trees have instead been planted in oversized containers that can be removed when necessary, such as during large events.

Along the Promenade, several hundred metres farther from the city centre, a traffic lane was removed to widen the pavement and make room for trees. Franz Gruber, head of St Pölten’s climate coordination office, said the trees would grow considerably in the coming years and eventually shade the entire street, bringing significantly cooler temperatures.

The pavement was built with paving stones that allow rainwater to seep into the ground. Rain falling on the road is also directed onto green spaces to water the plants rather than into the drainage system. In winter, when roads must be salted because of the risk of frost, meltwater is sent into the drains.

At Europaplatz, an artwork known as the Windfänger was installed during the square’s redesign in 2022. The five-metre-high open rotunda, which has a diameter of 13 metres, is intended to function as an oversized air conditioner. Water drips over more than 16,000 clay tiles, keeping them wet as it evaporates. The open structure allows wind to pass through and, ideally, carry cooler air towards the city centre.

Martin Gruber-Dorninger of St Pölten’s climate coordination office said the artwork did not measurably cool the city as a whole, but that its cooling effect was immediately noticeable when standing a few metres away. He said the water used by the Windfänger also seeped into the ground and watered nearby plants.

The city’s 2025 climate analysis found that St Pölten has a functioning network of corridors for cool air. These unobstructed routes include the Westbahn railway line and the Traisen, allowing cool air masses to flow into the city. The climate coordination office said the findings would be incorporated into land-use and development plans so that natural cooling effects could continue to be used.