Bonn is installing a city-wide network of 65 climate sensors that continuously measure air temperature and relative humidity on site. The network complements the city’s model-based urban climate analysis and, for the first time, provides real-time data on thermal conditions at specific locations. Sensors are placed both at heat hotspots and at cooler places that residents can use on hot days.
What changes
The existing urban climate analysis is based on climate models and examines the conditions on June 21, the day with the highest solar radiation of the year. It is used to evaluate thermal stress and spatial patterns such as heat islands and areas of cool air across the city. According to the city, this model-based analysis complies with the nationally established standard for assessing urban climate conditions. The new sensors add measured, on-site data to this modelled picture.
Where the sensors go
The 65 sensors are being installed gradually throughout the city. 36 measurement points are already in operation, and the complete network is due to be in place by the end of 2026.
| Location type | Sensors | Purpose |
|---|---|---|
| Cool spots (public green spaces and similar areas) | 55 | Show residents where conditions are cooler |
| Heat hotspots identified in the analysis | Remaining sensors | Measure the actual heat stress on site |
The measurement data is intended to let residents check conditions at the cool spots at any time and seek out cooler places on hot days. The sensors are mostly mounted on street lamps and trees. At the cool spots, they were placed in heavily shaded areas to capture the local cooling effect.
How the data is used
The data is integrated into the City of Bonn’s Urban Data Platform (UDP). A geoportal map shows the sensor locations and current temperature readings. The detail view of a sensor also shows humidity and, at selected locations, air pressure. A dashboard allows retrospective analysis, so daily trends and longer-term developments over several months can be tracked at all measurement locations.
Background
The city’s climate page describes Bonn’s urban climate as warmer, less windy and drier than the climate of open countryside. It also records a clear upward trend in the number of summer days above 25 °C and hot days above 30 °C in Bonn. Based on the urban climate analysis, the city has made projections of heat development up to 2035 under weak and strong climate change scenarios.