Over 4,000 fire fighters are battling a huge forest fire in north China with 2,000 or so more on their way, local authorities said Sunday.

The fire was spotted at 1:40 p.m. Saturday in Greater Hinggan Mountains in Inner Mongolia Autonomous Region, and spread to neighboring Heilongjiang Province about two hours later, according to officials of the forestry departments of Inner Mongolia and Heilongjiang.

"The fire is still raging. The area has had little rain and the temperatures have been higher than usual," Li Shuming, deputy chief of Heilongjiang Forestry Department, said Sunday.

The region's rainfall from June 22-26 was 42 to 100 percent less than that of the same period last year while temperatures were three to eight degrees centigrade higher, according to the Inner Mongolian Meteorological Bureau.

"This summer is the hottest as far as I can remember," said Xu Hongmei living in Hohhot, capital of the Inner Mongolia Autonomous Region. "I don't dare to take my 10-year-old son out, I'm afraid we'll suffer from heat stroke."