"Historically, about two-thirds of all general aviation (GA)
accidents that occur in instrument meteorological conditions (IMC)
are fatal -- a rate much higher than the overall fatality rate for
GA accidents."
Source: From the newly-released 80-page NTSB
study outlying the NTSB's thorough investigation of 72
weather-related general aviation accidents. The Safety Board also
issued six formal recommendations to the FAA on ways to prevent
weather-related general aviation accidents -- including better
initial and recurrent pilot training, and more thorough weather
briefings.