Look to the sky for Expo weather    

Visitors to the World Expo 2010 can get the latest weather forecast by just looking up at the old power plant chimney on the Puxi side of the site, the highest spot on both sites.

The 165-meter chimney of the 110-year-old Nanshi Power Plant has a LED screen which will display real-time temperatures.

The top of the chimney will change colors to indicate weather conditions and alert visitors to bad weather.

The old chimney, which sits along the Huangpu River will be known as the "Expo Thermometer" when it starts operating today.

The chimney is connected to the Shanghai Meteorological Bureau, which will provide precise weather forecasts for the Expo every hour as well as issue advanced weather alerts during the 184-day event.

The chimney has six weather colors - white means "good weather" (sunny and cloudy) and purple means "bad weather" (rain or snow). Blue, yellow, orange and red mean four levels of weather alerts. Red is the most serious. Patterns will be displayed on the body of the chimney during weather alerts to indicate what kind of bad weather is coming.

The chimney will operate from 9am to 10pm during the Expo; the site operates from 9am to 12am.

The bureau has built 26 observation points around the Expo site at different heights to help predict the weather on the 5.28-square-kilometer site, said Chen Zhiqiang, the senior bureau engineer in charge of weather forecasts for the Expo site.

The bureau has also assigned six chief service officers and 10 assistants to coordinate with the Expo headquarters.

Weather forecasts and alerts will also be broadcast and displayed on large screens across the site.

The chimney will also be illuminated to become a light sculpture at night. Colorful beams will form different three-dimensional structures, wrapping around the chimney.

The illumination was planned and provided by French city Lyon, which is famous for its energy-efficient street-lighting systems, as part of its Urban Best Practices showcase.