In the past there have always been weather enthusiasts interested in measuring weather in their direct environment.
Innovations in Internet of Things (IoT) have made it possible for sensor measurements to be easily collected and visualized on various online platforms. We currently verify the quality of crowdsourced weather data, specifically from Personal Weather Stations (PWSs) and from smartphones.
The network of PWSs in the Netherlands is already far denser than the network of KNMI’s automatic weather stations and continues growing. Though metadata on PWS-stations is often lacking, the measurements could be used as a complementary source to the high quality KNMI observations. Rainfall data at the resolutions generated by the PWS-network could specifically be useful for urban hydrological applications. For this purpose, the quality of these measurements is investigated. The often low-cost sensors linked to online platforms are compared to gauge-adjusted radar rainfall data. Additionally, the sensor performance of the most common type of PWS is evaluated in an experimental set-up next to a high-quality KNMI rain gauge. This minimizes measurement errors due to a faulty setup that are likely to occur in crowdsourced stations. Results show that, though sensor performance was relatively good, large differences in datasets can occur due to rounding in transferring data between internet platforms. This is the first aspect to address in order to make optimal use of crowd-sourced weather data. Overall we find that PWSs can provide useful rainfall information, and therefore hold a promise.
We also investigate the use of smartphones to monitor the weather. Battery temperatures were collected by an Android application for smartphones. A straightforward heat transfer model is employed to estimate daily mean air temperatures from smartphone battery temperatures (see Figure 2; Te, Tb and Tp represent the temperature of respectively the environment, body and phone. ke and kb describe the isolation between phone and environment and body respectively, while Pp is the thermal energy generated by the phone)  The results demonstrate the potential of smartphones to obtain weather information.
 de Vos, L., Leijnse, H., Overeem, A., and Uijlenhoet, R.: The potential of urban rainfall monitoring with crowdsourced automatic weather stations in Amsterdam, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-505, in review, 2016.
 Overeem, A., R Robinson, J. C., Leijnse, H., Steeneveld, G. J., P Horn, B. K., & Uijlenhoet, R. (2013). Crowdsourcing urban air temperatures from smartphone battery temperatures. Geophysical Research Letters, 40(15), 4081-4085.
Internet platforms used for crowdsourcing: