BEIJING, Oct 24 — Last Monday evening, a remarkable tidal event unfolded along eastern China for over 20 hours, leading to extensive flooding in coastal regions of Liaoning, Hebei, and Tianjin.

When the tide started rising in the Bohai Sea, residents expected a typical tidal surge, but water levels exceeded the norm by about 1 metre in several areas.

"In the absence of obvious wind and waves, a sudden increase in water levels over such a large area has never been recorded either domestically or internationally,” Fu Cifu, head of the Storm Surge Forecasting Office at the National Marine Environmental Forecasting Centre, told China’s state news agency Xinhua on October 22.

The phenomenon also triggered reverse flows of seawater down the coast, affecting provinces as far south as Jiangsu and Fujian, the South China Morning Post (SCMP) reported today.

According to the Hong Kong newspaper, the rising water levels saw residents post videos on social media depicting submerged roads where some jokingly compared their flooded neighbourhoods to Venice.

In cities like Dalian, Yingkou, and Jinzhou, the rising water levels resulted in mass evacuations to higher ground.

China’s Ministry of Natural Resources initiated a level-4 emergency response for marine disasters and deployed five teams of experts to assess the high water levels and evaluate the damage in affected regions.

"This serves as a reminder to us. In the context of global climate anomalies, extreme weather events may arrive quietly without any warning,” Fu was quoted as saying by the SCMP.

So, what caused the unusual flooding?

SCMP cited an amateur meteorological group, "China Weather Fans,” explaining that the tidal phenomenon resulted from a rare mix of astronomical and meteorological factors.

"Firstly, October 20 marked the strongest astronomical tide of the year. Secondly, the recent super moon just ended, raising tide levels by an additional 20cm.”

An unnamed expert from the Ministry added that the unusual rise was largely due to "warm, moist air flow collided with a cold front, forming a cyclone that caused an advance storm surge.”

The tidal floodwaters were reported to have only receded in severely affected areas like Panjin City yesterday.

According to the SCMP, there were no reported casualties.