Aachen Weather Beacon, Weather beacon at Haus Grenzwacht, Aachen, Germany

The Aachen Weather Beacon is an 11-metre illuminated column on the roof of Haus Grenzwacht, a municipal administration building at Aachen's main station. Its metal frame carries 180 fluorescent tubes: white ones on the shaft and white, yellow and blue ones on the sphere. The sphere's colour and the shaft's light sequence show the next day's forecast.

The weather beacon was added in 1958 to Haus Grenzwacht, which was originally built in 1924 by architect Emil Fahrenkamp. The building underwent later changes before the lighting system for forecasting was installed on its rooftop.

The beacon emerged when cities were finding new ways to share information with residents through simple visual signals. The colored lights offered people in the neighborhood a quick way to check forecasts without needing a radio or newspaper.

The column stands on the roof of Haus Grenzwacht, the municipal administration building at the main station, reaching 40 metres above the station square. It is switched on at dusk and off after sunrise, so evening is the time to read it. The display is controlled by the STAWAG network control centre using data from the German Weather Service in Essen.

The system runs on a simple color logic that many residents could memorize, turning it into a kind of visual language for the neighborhood. This ability to read the weather from outside proved especially valuable before mobile phones became common.