SHIJIAZHUANG -- North China's Hebei Province said it will help Beijing keep the weather under control for the 2008 Olympics with 84 rocket launchers to blast threatening clouds out of the sky.

During the Games, an arsenal of rockets and cannons will be arranged on "three lines of defence", between 15 and 120 kilometers from Beijing, to prevent rain from marring the opening and closing ceremonies.

August is Beijing's rainy season and the opening ceremony scheduled for the eighth and the closing ceremony on the 24th face a 50-50 chance of rainfall, according to experts.

The Olympic rain-prevention scheme will involve four cities in Hebei Province, including Zhangjiakou, Baoding, Chengde and Langfang, as well as parts of the neighboring Tianjin Municipality.

Beijing, which is chronically short of water, is well practiced at blasting clouds to prompt a much-needed downpour.

Between 2003 and 2006, the city's 26 rain-making stations boosted local reservoirs an average of 212 mm (8.35 in) of rain water, or 12 to 15 percent, according to Zhang Qiang, vice-director at Beijing's weather manipulation office.

Rain-prevention techniques, however, are still in the testing phase.

Beijing held rain-prevention tests this summer, firing silver iodine or similar catalysts from artillery or rockets, based on the theory that the chemical will cause the rain to fall while the clouds are still a long way from Beijing.

Zhang said the catalysts have no direct impact on the environment as long as the doses are kept within 0.5 gram per square kilometer.