At nine in the morning it is already 29 degrees Celsius in Berg am Laim, a district of Munich. Markus Striese of the association München Aktiv für Gesundheit points a surface thermometer at the asphalt: 35 degrees in the shade, 42 in the sun. That seven-degree gap across a few metres is why German cities are now building an unusual kind of infrastructure — maps of shade.
Striese's association developed the web application "Hitzefrei" for exactly this. Enter a start and a destination and it returns not the shortest route but the shadiest one: the software uses building data and the position of the sun to work out where shadow falls at a given time of day. Cool places such as churches, shaded benches, drinking fountains and public toilets are marked as well. The walk sometimes gets longer — but more bearable.
From a volunteer project to city hall
What began as a health association's idea is now official policy too. Munich's public health department, working with the municipal geodata service, has published an interactive map of cool places: parks and green spaces, the city's bathing lakes, publicly accessible cool interiors, plus drinking fountains and toilet facilities with water dispensers. It forms part of the city's heat protection strategy and is being expanded continuously.
The intended audience is precisely chosen. The map is aimed explicitly at people travelling on foot, by bicycle or by public transport — those least able to escape the heat. Anyone sitting in an air-conditioned car has no need of a shade route.
Alongside these, freely available tools exist that are not tied to a single city. The web applications Shadowmap and ShadeMap render the sun's path as a map and show which streets, courtyards and stretches of park lie in shadow at which hour; ShadeMap also reports how many hours of sun or shade a given spot receives over a day or a year.
None of these tools cools a city down. What they do is make visible what is already there — and supply the argument for the next step. Where a map shows nothing but gaps, trees, shading and green space are missing. "That shows we need more green space and more shade in the city," Striese says. In the middle of a heatwave pushing towards 40 degrees, that is no longer an abstract demand.