After boarding the passenger, we ramped out and I ordered the F/O to set flap 5. While I was confirming, ATC gave us information concerning a thunderstorm 5 miles south of airport and I missed checking the Flap setting. After lining up the aircraft for a standing takeoff, I pressed the TOGA switch and as soon as the throttle advanced forward, the Takeoff warning was activated simultaneously, so we rejected the takeoff. After applying immediate action, the rolling distance was only 1~2 m and brake temperature was in normal range. So I set the flap at the appropriate position and proceeded with the normal operation. Reports on Rejected takeoff due to missed flap setting are occasionally reported. Most of the time this happens when multiple situations occur while crew are in the middle of performing normal procedure during a short taxiway to the runway, which affects the normal takeoff. Therefore whenever the situation is busy, complex, or the taxiway to the runway is short, the pilot should stay composed and try to ensure there is enough time for normal procedures.4. What should a pilot do in a complex situation according to the passage?