Simulation of the natural environment provides more realistic training in flight, ground, ocean, and littoral domains. The effects of illumination, cloud cover and physics-based smoke affect the ground forces. Winds aloft, pressure and temperature variations, turbulence, precipitation, clouds, and icing characteristics affect the flight domain. Realistic surf zone, open ocean and ship dynamics enhance the marine simulation. These richer dynamics increase the quality of training for the warfighter. The establishment of the Environment Federation allows more standardized weather information to be available at each federate through the HLA, but how each federate uses this information is not standardized. This paper describes the implementation and use of STOW97 and ModSAF Synthetic Natural Environment capabilities, and the EnviroFed paradigm, in a real-time simulation system. Various capabilities, including pressure barometer simulation and localized weather, as well as fair-fight correlation issues between live, virtual, and constructive forces, are discussed.