Xinyi, a small, county-level city in Maoming received 429.5 millimetres of rainfall in just six hours, according to the provincial flood control and drought relief headquarters.
Eight people died and four others were reportedly missing in Xinyi.
The provincial civil affairs department has declared the second highest state of emergency and dispatched working teams to Xinyi.
Relief supplies including 200 tents and 10 tonnes of rice have been sent to the disaster-hit areas, state run Xinhua news agency reported.
The rainstorm abated yesterday afternoon and stopped in the evening. But local authorities still warned of geological disasters in mountainous area.
PTI