An article in the Los Angeles Times notes that the Chinese are planning to keep rain away from the roof-less Olympic stadium—by force if necessary.
The Chinese are planning on using "cloud seeding" to ensure good weather. To do this, they have farmers sitting not too far from Beijing with anti-aircraft guns. When the farmers see a cloud that looks like it might rain, they fire silver iodide into it. The particles of iodide makes the cloud's moisture condense around them, creating rain.
That's not all China has up its sleeve. In the Mother Jones January/February 2008 issue we noted Chinese plans for "rainmakers" and a new, low-emissions, public transit system for the Olympic village.
For more on Beijing's attempt to make 2008 Olympics go off without a hitch (or a CO2 emission), check out Beijing Goes Green.