Large swathes of China’s central Henan province were under water on Wednesday, with at least a dozen people dead in its capital Zhengzhou after the city was drenched by what weather watchers said was the heaviest rain in 1,000 years, Reuters reported.

With more rain forecast across Henan for the next three days, the government of Zhengzhou, a city of over 12 million on the banks of the Yellow River, said 12 people were reported to have died in a flooded subway line, while more than 500 were pulled to safety.

About 100,000 people in the city have been evacuated to safe zones.

Roads in a dozen cities have been severely flooded.

Video on social media on Tuesday showed commuters chest-deep in murky floodwaters on a train in the dark and an underground station turned into a large, churning pool.

From the evening of Saturday until late Tuesday, 617.1 millimeters (mm) of rain fell in Zhengzhou, about 650 km (400 miles) southwest of Beijing. That’s almost on par with Zhengzhou’s annual average of 640.8 mm.

“Flood prevention efforts have become very difficult,” Chinese President Xi Jinping said on Wednesday, addressing the situation in a statement broadcast by state television.