Urban areas change their own climate most famously by creating an urban heat island (UHI) and by introducing mechanical drag on air flow and moisture transport within the city. They also emit pollutants that have strong negative local effects. In order to understand and model these effects, we need comprehensive measurements of temperature, moisture, rain and wind in urban areas. We are using Waggle to build an urban Weather Sensor Network (WxSeNet or “wexy-net”), taking advantage of ubiquitous wireless communication technologies to enable continuous monitoring of the urban atmosphere from many dozens or hundreds of WxSeNet nodes. The information gathered will be used to validate and improve models of the urban-weather and urban-climate system.