Heavy rain is forecast for some areas affected by Monday's magnitude-6.6 earthquake in Northwest China.

The rain, combined with the continuing aftershocks in the area, could be dangerous, experts warned.

Sun Jun, chief forecaster of the Central Meteorological Center, said sunny weather will continue on Tuesday in Dingxi, Gansu province, but on Wednesday evening, most of the city will have moderate rain, and a few places will have thunderstorms.

The weather forecasting station in the provincial capital, Lanzhou issued a red alert for rainstorms on Monday. Red is the highest level of China's four-color weather alert system.

Sun said that people in quake-affected areas should be on alert during rainy weather and should not set up tents under trees or electric line poles "which are easily struck by lightning".

As of 4 pm on Monday, 411 aftershocks had been recorded in the zone, with the strongest at magnitude 5.6, according to the Earthquake Administration of Gansu.

Experts said landslides and flash floods also are a danger.

Minxian and Zhangxian counties in Gansu, which were struck by the earthquake at 7:45 am on Monday, are part of the Lanzhou-Tianshui seismic zone, a mountainous area prone to landslides and floods, said Chen Huizhong, research fellow at the Institute of Geophysics of the China Earthquake Administration.

"There have been many major earthquakes in the zone, which has been one of the 23 major seismic zones in China since ancient times," he said.

On July 21, 1654, a magnitude-8 quake jolted Gansu, with Tianshui as the epicenter. Aftershocks followed for more than 100 days.

"Twenty-five quakes with or above magnitude-5 have occurred in areas 200 km from Minxian and Zhangxian since 193 BC," Chen said.

"China has a high incidence of earthquakes. Since 1900, earthquakes have killed 550,000 people, accounting for 53 percent of the deaths from earthquakes worldwide," Chen said.

"In the Tangshan earthquake in 1975 alone, 240,000 people died," he said.

Chen said earthquakes take place in five major areas in China: Taiwan and its adjacent waters, Southwest China, Northwest China, North China and eastern coastal areas.