Beijing's observatory issued an orange alarm Wednesday as heatwave swept across the city.

Tourists walk with fans against sunshine in Beijing, cpital of China, Aug. 12, 2009. [Xinhua]

The city registered the highest temperature of 38 degrees Celsius in Haidian District at noon, just five days after the lunar-calendar autumn began.

The alert is the highest of its kind Beijing has ever seen in the same month over the past years.

Local residents always expect a cool climate in the autumn and describe unexpected heat during the period an "autumn tiger."

Many pedestrians, cyclists and tourists had to hold up umbrellas to avoid the scorching sunshine and icecream peddlers said the business was very good.

The heat may continue on Thursday and Friday until the cold air from northwest brings thunderstorms, said the observatory.