With just 10 days to go before the opening of the Beijing Olympics, the Games' organizers, who seem to have had everything under control, have to face an uncontrollable challenge -- the weather.

While a whole week of hot and humid weather with no rainfall and a persisting haze dampened people's mood and undermined a newly-built confidence in the city's air quality, a "weather modification" project is also underway to guarantee that the Games' opening ceremony won't be spoiled by a downpour.

Tipped by meteorologists and scientists, officials of the Beijing Olympic organizing committee now pin their hope on the arrival of "Liqiu", a term on the Chinese lunar calendar which literally means "the beginning of autumn," on Aug 7 and the state-of-the-art weather engineering technologies.

"Starting from Aug 7, the weather of Beijing will gradually enter the best period of the year, with both temperature and humidity on the drop, and air quality on the rise," Guo Wenli, director of the climatic center under the Beijing Municipal Meteorological Bureau, told Xinhua on Monday.

The past week from July 21 to 27 recorded an average daily temperature of 27.4 degree Celsius for the Beijing region, 1.9 degrees higher than the average level in the previous years, according to the meteorological bureau.

Adding to the woe was a rare absence of wind throughout the week, which led to the accumulation of particulate matters in the air and the forming of the haze that severely crippled visibility, said Guo Hu, head of the Beijing Meteorological Observatory.

When the Olympic Athletes' Village opened to athletes, coaches and officials from all over the world on Sunday, some foreign athletes were conspicuously missing from their delegations that checked in the village. They chose to stay in Japan or South Korea for training till the last minute, reportedly for fears of the city's "filthy air."

Han Song, a writer with an office on the 15th floor of a high building near Xuanwumen in central Beijing, took a picture of the city through his office window every morning in the past week, only to find the city shrouded in haze all the time.

Astonished and disappointed, Han wrote in his blog: "Is this what we got, seven days after we pulled half of the city's cars out of the roads?"