Weather simulation is a modular addition to a digital radar landmass simulator (DRLMS). The DRLMS is a four channel system, i.e., culture, elevation, aspect and weather. All four channels are integrated to provide a simulated radar landmass simulation with weather. Implementation entails the full or partial occultation of terrain and targets by weather and vice versa. Weather mass is simulated in three dimensions; that is, it has a bottom and height. The weather mass is not made of simple geometric objects. Weather maps can be loaded into the system as weather patterns, and the weather patterns can be expanded, rotated and translated. In addition, the weather channel can be used to simulate chaff and jamming patterns.