The flight crew of the business jet were approaching the destination airport near the conclusion of the transcontinental flight. The second-in-command (SIC) reported that air traffic control cleared the flight to land when the airplane was about 3 miles from the airport. Just after being cleared to land, the air traffic controller informed the flight crew that heavy rain would be encountered throughout the landing approach. The pilot-in-command (PIC) also described observing precipitation via weather radar and that a heavy rain cell had been reported on the runway. The SIC subsequently called the runway in sight when the airplane was about 250 feet above the airport elevation, and they continued the approach. As that airplane entered the landing flare, the forward visibility was extremely reduced, due to the heavy rain downpour, and the flight crew lost outside visual reference. Shortly after touching down the crew regained visual reference of the runway and realized that the airplane was drifting right of the runway centerline. The airplane continued right and the right main landing gear exited the paved runway surface into the grass. The pilots applied left control inputs, and the airplane rotated about 70° to the left before it came to rest on the runway, oriented nearly perpendicular to their approach path. The flight crew then applied power and were able to taxi to parking uneventfully. The airplane sustained substantial damage to the right wing during the accident sequence. The PIC reported that there were no preaccident mechanical malfunctions or failures of the airplane that would have precluded normal operation. A review of weather radar reflectivity data about the time of the accident showed that heavy to extreme precipitation was present on the approach to and over the airport. A special surface observation report was issued about the time of the accident and indicated ¾ statute mile of visibility in heavy rain, thunderstorms, and mist. Review of airport surveillance video confirmed that when the accident airplane was landing, the runway approach end was obscured by heavy rain, consistent with the flight crew, radar, and airport surface observation report. After the accident, the PIC stated, “We didn’t like the looks of the radar return, however there were no indications of sheer and the two aircraft ahead of us reported no issues. We flew a stabilized [instrument landing system] approach all the way to touchdown, but the visibility through heavy rain, gusty winds and wet runway condition should have been anticipated.”