In this report the work with simulation of different sensor systems in various weather conditions is described. The sensors studied in this report are IR, laser and radar. Different tools have been used to simulate the different sensors and these tools are integrated in MSSLab. MSSLab (MultiSensor-SimulationLab) is a simulation laboratory where advanced sensor systems can be simulated in various environments. In the introduction there is a short overview of different weather conditions and how they affect optronic and radar sensors. Four weather conditions (cases) are specified: mostly sunny, rain, cloud and snowfall. These cases will be used in the future work to study how a UAV with its sensors is af-fected in the different weather cases. In the report there is also a description of the studied UAV and its approach to specific target areas. For simulation in thermal IR and visual wavebands the multispectral software suit "CameoSim" is used. The atmospheric transmission used by CameoSim is calculated in MODTRAN (MODerate spectral resolution at-mospheric TRANSsmittance algorithm and computer model). With MOD-TRAN the transmittance can be calculated for the different weather cases. A 3D-laser model developed at the FOI has been used to simulate laser sensors. In this model there is currently no possibility to simulate atmo-spheric transmission. However, with data from MODTRAN the influence from atmospheric transmission can be handled in the laser sensor simula-tions. The ray tracing software tool "SE-RAY-EM" is used for radar simulations. This software is now complemented to handle both damping and scattering for the different weather cases. Some methods of how to achieve a common modelling of the weather influence on all sensors in the simulations are also described in the report. Preliminary IR and radar simulations have been made for the different weather cases and ranges up to a few kilometres. The results show that clouds heavily degrade the IR-performance, whereas weather influence on the simulated radar system is moderate.