To improve environmental monitoring, the availability of great coverage of spatiotemporal data in an interoperable way is crucial for its integration into environmental models, for example, to compute fire danger models. To produce up-to-date and accurate results those models need the availability of data with high temporal and spatial resolution. Thus, it is promising to consider the increasing number of in-situ sensors providing observations of our environment in real-time. Today, interoperable access to such spatio-temporal data is achieved by Geospatial Information Infrastructures (GIIs). From a technical point of view GIIs provide this data through standards-based Web service interfaces. While those Web service interfaces already enable the interoperable discovery and retrieval of sensor observations, the functionality to publish sensor observations is still an arduous task. Hence, in this paper, we present an approach to improve the registration of sensors and the publication of their observations via standards-based Web service interfaces. We evaluate our approach by extending a standards-based GII and by applying the developed approach to the example of integrating in-situ weather observations into the European Forest Fire Information System for assessing fire danger in Spain.