Dianmu reached its maximum intensity as its winds reached up to 285 km/h (180 mph) and the barometric pressure fell to 915 millibars. The JMA assessed the typhoon attaining a 10-minute peak of 185 km/h (115 mph) winds. After maintaining Supertyphoon status for 42 hours, the storm began to weaken as it swung westward. The typhoon briefly regained supertyphoon status on June 18 before finally weakening again a few hours later. The next day, Dianmu swung northward as the center was located southeast of Okinawa. As it turned northward, dry air entered the storm causing the center to become ragged and eventually resulted in the storm weakening further as the winds dropped to on June 19.