Visitors to Expo 2010 Shanghai are expected to have a few cool days coming up, with organizers vowing to provide more shelters and ease the surging crowds waiting outside popular pavilions.

The mercury in Shanghai will hit 28 C on Tuesday and rainfall is forecast for the next two days, but organizers said they will continue to adopt measures to cool down the heat.

"We will focus on installing shelters in front of popular pavilions. Hundreds are now being installed every day," said Hong Hao, chief of the Expo Coordination Bureau. "The aim is to guarantee a comfortable visiting experience before the extreme heat approaches in July."

Hong also promised better air conditioning, additional drinking supplies and having cooling facilities running before the Expo Garden opens.

Visitors to the Expo on Monday complained about their discomfort under the sizzling sun. The highest temperature reached 30 C, while visitors found few shelters outside some of the most popular pavilions like Japan and Saudi Arabia. Twenty visitors were sent for medical treatment suffering from heatstroke.

"Hours of walking in the Expo Garden can be very exhausting," said 53-year-old Pene Brown of Australia, who planned her trip to China especially for Expo Shanghai 2010. "The exhibition was an excellent one, but we have decided to retreat because of the heat and our fatigue. We'll watch the rest of the show on TV."

Brown's move explains the decreased number of visitors on May 3. Some 130,000 had entered the Expo Garden by 4 pm, while the number was 200,000 in the previous two days.

A visitor surnamed Zhang with his 18-month-old baby gave up queuing for the Japan Pavilion, which required a three-hour wait in the sun, as he was afraid the baby could not stand the heat.

From time to time, people escaped from the crowd because of the discomfort caused by the heat and congestion. Staff and volunteers quickly stepped in with first-aid assistance.

Visitors who decided to stick it out tried every means to escape the heat, by standing in the shadow of buildings and under umbrellas and sunshades. Many used the free Expo map to fan their hot faces.

Among tens of thousands waiting, 63-year-old Huang Xin was better prepared for the occasion. Fully equipped with sunglasses and cooling oil, Huang's one-and-a-half hour queue for the Germany Pavilion was easier to endure.

The ease of his wait was due to the design of the Germany Pavilion. Marion Conrady, press officer for the Germany Pavilion, told China Daily that the structure of the pavilion created a 383-square-meter shaded area for waiting visitors, blocking 90 percent of the direct sunlight.

The France Pavilion and Meteorology Pavilion also turned on their cooling systems to create a cooler environment for visitors lining up in front of their doors.

In the rest of the garden, water sprayers are being utilized on the squares and overhead pedestrian paths in the 3.28-sq-km area to provide some relief from the heat. Officials said that the temperature will drop 6 C after 15 minutes of spraying.

Medical treatment for heatstroke will be available, and more medical staff will be on hand, as well, authorities said.

Shanghai will enter the rainy season in early June. Necessary measures have been taken to handle all types of weather, Hong said.