The meteorologists say they can force rain in the days before the Olympics, through a process known as cloud-seeding, to clean the air and ensure clear skies. China has been tinkering with artificial rainmaking for decades, but whether it works is a matter of debate among scientists.

Weather patterns for the past 30 years indicate there is a 50 percent chance of rain for both the opening ceremony on Aug. 8, 2008 and the closing ceremony two weeks later, said Wang Yubin, an engineer with the Beijing Meteorological Bureau.

The forced rain could also help clean Beijing's polluted air, said Wang Jianjie, another meteorologist with the bureau.

"When conditions permit, we will artificially increase rainfall," she said. "Rainfall is a way to naturally clean the air."

In 2003, the U.S. National Academy of Sciences questioned the science behind cloud-seeding as "too weak." But China frequently uses artificial rainmaking in the drought-plagued north.

Last May, Beijing boasted having generated rainfall to clear the air and streets following the worst dust storm in a decade.

Technicians with the Beijing Weather Modification Office said they fired seven rocket shells containing 163 cigarette-size sticks of silver iodide over the city's skies. They claimed it provoked a chemical reaction in clouds that forced four-tenths of an inch of rain.