San Francisco  - The normally blue skies of north California were thick with smoke Thursday as more than 1,000 forest fires burned across the region.

The authorities in many areas warned of "unhealthy" air quality, the San Francisco Chronicle reported under the headline "Having a Bad Air Day."

An army of firefighters with support from the neighbouring states of Oregon and Nevada were battling the flames that were ignited by a series of lightning strikes over the weekend.

California Governor Arnold Schwarzenegger visited affected areas along the popular coast road in Big Sur and Chico on Wednesday. Schwarzenegger said that nobody thought that there could be so many fires.

He called on people not to buy fireworks for the traditional July 4 US Independence Day celebrations, as it was too dry and too dangerous to set them off.

Earlier this month, Schwarzenegger had declared a state of emergency in California because of the dangers related to the dry weather.

In the Mendocino region alone, more than 130 fires were burning, forcing hundreds from their homes.

Initial reports were of little damage to property.

Moister, cooler air was heading towards San Francisco from the north on Wednesday.

"We're doing a little bit better," Fire Division Chief Wayne Connor said. Humidity is up and winds are down, he said, adding "We're digging a lot of fire line." (dpa)