"The forecast for the opening ceremony shows showers and possible thunderstorms," said Wang Jianjie, deputy director of the Beijing Meteorological Bureau.

At the same time, typhoons may hit other host cities - including Hong Kong.

"We can only speak about the possibility," Wang said yesterday. "With the current technology, it's impossible for us to tell when and where the rainfall will be."

Opening ceremony organizers said they would have to cancel fireworks in the event of persistent heavy rainfall.

The Hong Kong Observatory also predicts rain during the first few days of the equestrian events. Even a typhoon is possible.

Meanwhile, Secretary for the Environment Edward Yau Tang-wah said Hong Kong's two power companies have been urged to use more natural gas to generate electricity to reduce emissions during the period. Hongkong Electric and CLP have agreed to increase natural gas use by 20 percent throughout the equestrian events, a government spokesman said yesterday.

Concerns for the health of Olympic riders and horses were raised after pollution levels hit record highs in Beijing and Hong Kong last week.

The inclement weather forecast will not stop the show, with weather watchers cooperating closely with organizers to help them make good decisions in the event of bad weather.

Meteorologists have, since July 25, been stationed at the Beas River and Sha Tin venues - where the cross-country, dressage and show-jumping events will be held - to provide weather reports.

John Breen, head of venue operations and communications center of the Equestrian Company, said while there may be delays, they will cancel an Olympic event "only in the most extreme circumstances."

He added the company has contingency plans for adverse weather, including liaising with public transport operators and keeping ticket holders informed of any plans to delay or postpone competitions.

The organizers can accommodate up to three days of delays in the event of signal 8 typhoons or other weather conditions deemed serious enough to postpone any of the competitions.

There will be 73 horses in the cross- country races on August 10.

"It will be a logistical nightmare [to have to postpone or cancel an event like this]," said Leo Jeffcott, veterinary technical delegate to the equestrian events.

Heat is more of a concern for the horses. To prevent horses from overheating, he said: "We will have misting tents, blow cold air and pour cold water on the them, until we get their temperatures down."

Meanwhile, Beijing's air quality fell in line with the World Health Organization recommendations for the third straight day yesterday, two weeks after the city pulled cars off the roads and closed factories to curb pollution. The air pollution index around the main Olympic venue was in the "excellent," category in the 24 hours to noon, the first time this year the index stayed below the WHO's recommended maximum for more than 72 hours.

Officials said they might take more cars off the roads and shut another 105 factories if there is "extreme" pollution during the Games.