As Khanun forms, China warns of third typhoon in three weeks

BEIJING, July 29 (Reuters) - Chinese forecasters on Saturday warned of the approach of Tropical Storm Khanun, expected to rapidly gain typhoon strength and strike China's densely populated coast sometime next week.

Khanun, now more than 1,000km (620 miles) east of the Philippine archipelago in the Pacific, may make landfall in China's economically important Zhejiang province as early as Tuesday, Chinese forecasters said.

Typhoons, as hurricanes are called in East Asia, are common in China, often threatening big cities. As many as 150 Chinese cities suffer from flooding each year due to inadequate drainage systems, disrupting local economies and even claiming lives.

As the Western Pacific enters its peak typhoon season in August and September, scientists warn storms could grow more frequent and violent due to global warming. Khanun would be the third typhoon to hit China after the powerful Doksuri on Friday and Talim just a week earlier.

Global average sea surface temperatures hit 21 Celsius (69.8 Fahrenheit) in late March and remained at record levels for the time of year throughout April and May. In the Florida Keys last week, the surface ocean temperature soared to abnormally high levels.

Temperatures on land have also smashed records this year as heatwaves ravaged much of the Northern Hemisphere - from Canada and the United States to the Mediterranean, India and China.

A remote township in northwest China endured temperatures of 52.2C earlier in July, setting a new record for the country.