Weather is a major cause of aircraft accidents and incidents and the single largest contributor to air traffic system delays. Through improvements in the knowledge of current weather conditions and reliable forecasts, the Federal Aviation Administration (FAA) can improve aviation safety, increase system capacity, and enhance flight planning and fuel efficiency. The FAA's Aviation Weather Research Program (AWRP) was established to address specific requirements for weather support to aviation by providing the capability to generate more accurate and accessible weather observations, warnings, and forecasts and also by enhancing the scientific understanding of atmospheric processes that spawn aviation weather hazards. These research areas include inflight icing, ground deicing, turbulence, convective weather, oceanic weather, numerical modeling, ceiling/visibility, Doppler weather radar, and terrain-induced turbulence. This paper describes the activities and technological developments of the FAA's Aviation Weather Research Program.