Crowdsourced observations have the potential to bring a step-change in urban climatology. This rapid prototyping project explores their potential for improving the standard observed grids, and the likely consequences for urban climate services. Basic quality control procedures are applied to WOW, Davis, Netatmo and Met Office sites around Manchester (UK), and site records of daily minimum and maximum temperatures are built. These are interpolated onto a set of daily observed grids of temperature for Manchester at 1km resolution for summer (JJA) 2020, thus obtaining a crowdsourced alternative to HadUK-Grid. The number of tropical nights (minimum > 20 degrees) is counted in these two gridded products. This provides the baseline for a current climate service for partners in local government that projects possible future changes in heat hazards. Thus the comparison of the standard and crowdsourced products gives some insight into the potential for observations from citizen science to improve gridded observations, an observed hazard metric, future projections of that metric, and so influence public policy decisions related to extreme heat.