At least five counties and cities in Guangdong experienced heavy rainfall yesterday night, state run Xinhua news agency reported.
Haima made a landfall in Shanwei in the province yesterday, according to information released by local meteorological services.
It has weakened as it travelled further north, it said.
Shanwei disaster relief office said gales and rain from the typhoon has caused 59 dike ruptures, damaged 21 dam gates and 179 water facilities.
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Heavy rainfall has been forecast for the last two days in several cities.
He Guoqing, a senior official with the provincial disaster relief office, warned that the water level at most of the province's dam were at dangerous levels and the ground especially on mountain slopes, was still saturated from the last typhoon.
China had earlier issued a red alert and closed down offices, businesses and schools in the southern city of Shenzhen.