On June 20, the center of Dianmu bypassed Okinawa by to the east as the storm continued to weaken. Satellite imagery showed the storm losing its deep convection and significant outflow and its winds dropped to 145 km/h (90 mph). As the storm approached Japan, it interacted with a trough which was position northwest of the storm. The resulting interaction with the trough caused the storm to drop below typhoon status. As the storm edged closer to Japan, it began to gradually take on the characteristics of an extratropical cyclone before it made its first landfall in Shikoku before making its second landfall in Honshū on June 21. The Joint Typhoon Warning Center issued its final advisory on Dianmu at 1800 UTC while the JMA continued to issue advisories until June 23. The extratropical remnants of Dianmu then dissipated over the Bering Sea on June 25.