Initially moving northward, the cyclone turned westward in response to a building ridge to its northeast while slowly strengthening, reaching its peak intensity with maximum 10-minute sustained winds of 85 km/h (50 mph) on August 16.

At 20:05 UTC that day, the storm made landfall in Shanghai at peak intensity, maintaining its strength as it moved inland due to ample environmental moisture.

However, Rumbia began to weaken as it continued further inland, degenerating into a tropical depression on August 17 shortly before becoming extratropical over central China.

Rumbia, the third tropical cyclone to strike East China in 2018, succeeding tropical storms Ampil and Yagi, produced widespread heavy rainfall over regions already saturated by rains from the previous storms, causing flooding which claimed 53 lives and destroyed thousands of homes throughout the northeastern provinces of Anhui, Henan, Jiangsu, Shandong, and Xuzhou.

On August 13, 2018, the Joint Typhoon Warning Center (JTWC)[nb 1] began monitoring a weak area of low pressure to the south-southeast of the Ryukyu Islands.

[5] Curved rain bands signified increasing organization and the JTWC issued a Tropical Cyclone Formation Alert later on August 14.

Around 12:00 UTC, Kadena Air Force Base in Okinawa—roughly 80 km (50 mi) north of the system's estimated center—recorded sustained winds of 37 km/h (23 mph) and a pressure of 998 hPa (mbar; 29.47 inHg).

[15] Based on JMA analysis, Rumbia reached its peak intensity around 15:00 UTC just east of Shanghai with winds of 85 km/h (50 mph) and a pressure of 985 hPa (mbar; 29.09 inHg).

[16] At 18:00 UTC on August 16, a ship near the mouth of Hangzhou Bay reported sustained winds of 78 km/h (48 mph) and a pressure of 986 hPa (mbar; 29.12 inHg) within the cyclone's center.

[15] Shortly after reaching peak intensity over the Hangzhou Bay on August 16, Rumbia made landfall over Pudong New Area, Shanghai, China around 20:05 UTC, becoming the third tropical storm to hit the city in 2018.

[17] Despite moving over land, ample atmospheric moisture and low wind shear enabled Rumbia to maintain its strength as it progressed inland.

However, as the storm moved through the region rainfall far exceeded forecasts, prompting emergency warnings on August 18 to all residents downstream along the Mi River.

[20] Shanghai officials deployed 93,590 workers to quickly repair damaged infrastructure and placed an additional 127,031 rescuers on standby.

[21] Speed restrictions were implemented across roads in Jiangsu Province for high winds, with hundreds of personnel deployed to enforce them.

[23] In the weeks prior to Rumbia, the successive impacts of tropical storms Ampil and Yagi left the region saturated and unable to effectively absorb rain water.

Widespread torrential rains affected provinces unaccustomed to significant typhoon impacts: northern Anhui, Henan, Jiangsu, Shandong, and Xuzhou.

Rainfall peaked at 183 mm (7.2 in) in the Jiading District resulting in some flooding which affected three homes, twelve cars, and ninety-eight roads.

Storm- to typhoon-force winds battered coastal areas; a peak gust of 119 km/h (74 mph) on Gaogong Island in Lianyungang.

[35] As flooding overtook large swaths of Weifang, local fire and police departments were rapidly deployed to evacuate over 14,000 people trapped in submerged communities.

Ten disaster centers were established to coordinate relief efforts, provide medical care, and reduce the risk of post-storm diseases.