The Hong Kong Observatory forecasts a breezy day with the temperature ranging from 17 to 21 degrees Celsius and relative humidity of 70 to 90 percent. The Environmental Protection Department did not give an air pollution forecast but the recent index is about 70 to 100, which is regarded as high.

"The ideal temperature is 15 to 18 degrees. High humidity will be another problem for the runners," said William Ko Wai-lam, chairman of the organizing committee.

Ko said 500 first-aid workers will provide medical services during the race and more helpers will be stationed along tougher routes.

"Thirteen first aid stations and eleven water stations will be set up along the race routes to offer plenty of water and other support to runners," Ko added. He was confident there would be enough facilities to provide adequate replenishment for all.

The route will compel the temporary closure of roads including the Island Eastern Corridor from Sai Ying Pun to Sai Wan Ho, Nathan Road and routes from Tsim Sha Tsui to Ma Wan at various times. Closures start just after midnight and last until about 2pm, when the marathon ends. Also 161 bus routes and 27 minibus routes will be affected.

Police senior traffic officer Ho Ka- fai expected traffic jams at the Cross Harbour Tunnel, King's Road, Shau Kei Wan Road and Gloucester Road.

"We urge people if possible to avoid road transportation that might be affected by closures that day," Ho said. "If you must be on the road, please choose roads which will not be closed."

Rail services will start earlier from 3.25am for the Sheung Shui to Tsim Sha Tsui East route and also the Tuen Mun to Nam Cheong route, and at 4.05am for the Chai Wan to Sheung Wan route.

The first event is scheduled to start at 5.15am. All races will finish at the soccer pitch in Victoria Park. The events are the 10-kilometer race, the half marathon and the full marathon. This year is the 13th anniversary of the local marathon and the total prize money is US$100,000 (HK$780,000).