150+ cooling measures — 22 cool zones, ~100 mist stations, and up to ~4,500 trees planted per year; street trees cut daytime air temperatures by up to 1.2 °C (over 2 °C in shade).
Figures reported by the city programme, verified against published case-study sources.
Background
Vienna, consistently ranked among the world’s most liveable cities, is warming quickly and faces intensifying summer heat. Rather than a single flagship project, the city pursued a layered network of small interventions across public space.
The intervention
- Cool Streets: car-free stretches with shade, seating, and cooling elements; sensors release spray-cooling when temperatures exceed a set threshold
- 22 “cool zones” open in summer, roughly 100 mist installations, and ~1,600 drinking fountains
- Planting up to ~4,500 trees per year, green facades, and a goal of green space every 250 metres
Results
Research on Vienna’s nature-based measures found street trees lower daytime air temperatures by up to 1.2 °C, with over 2 °C of relief in shaded spots — with tree cover the single most effective measure. Roughly 85,500 m² of streets and squares have been greened.
Lessons
A distributed, repeatable toolkit — cool streets, mist, fountains, and above all trees — scales across a whole city and reaches people where they walk, complementing large green corridors.
