BEIJING — International Olympic Committee officials are monitoring the heat, humidity and air pollution levels to determine whether contingency plans need to be put into action during the Beijing Games.

After a weekend of blue skies, a haze returned over the city today, four days before the opening ceremony. Together with the sweltering temperatures and draining humidity, midday conditions for any physical activity were brutal.

IOC president Jacques Rogge, his face a blotchy red after attending an outdoor sponsor ceremony, said he was waiting for the latest weather and air quality data.

"I'm not an expert," he said. "I want to see the figures. We see the figures every day. I will get the weather forecast later."

IOC executive board member and marketing director Gerhard Heiberg said the issue should be discussed during the three-day IOC general assembly starting Tuesday.

"We are watching what's happening. Let's see," he said. "Yesterday was a wonderful day. Today, is it hazy? Is it pollution? I don't know at this stage. We are most concerned about the athletes."

Heiberg said the IOC meetings should cover the possible contingencies for the Olympic competition.

"I don't have any ideas at this stage," he said. "I want to listen and then find out."

Rogge repeatedly has said that outdoor endurance events lasting more than an hour, such as the marathon and road cycling race, could be postponed or rescheduled if pollution levels were too high.

Beijing's polluted air has been one of the biggest worries for Olympic organizers and prompted drastic measures earlier this month that included pulling half the city's 3.3 million vehicles off the road, halting most construction and closing some factories in the capital and surrounding provinces.

"As I said earlier, we can guarantee that we will provide good air quality to the athletes and officials and spectators based on the measures we have taken over the last 10 years," Beijing organizing committee spokesman Sun Weide said Monday. "We can assure quality air during games time."