Firefighters put out two grass fires Friday afternoon on Lime Ridge near Boundary Oak Golf Course in Walnut Creek.
On a dry afternoon, Contra Costa County Fire Protection District firefighters were assisted by air drops from California Department of Forestry planes.
No injuries were reported in the two-alarm fires, first reported at 3:36 p.m.
Some power lines were down in the area, but firefighters are unsure if that might have been a cause of the fires or if the lines fell after the fires began. The cause is still being investigated.
The fire moved close to some expensive homes in the Rancho Paraiso subdivision, but the blaze never threatened them.
One fire was small. A second one was two acres when firefighters arrived and grew to six acres before it was extinguished.
Lewis Broschard, public information officer for the Contra Costa Fire District, said the weather today and the dry grass on the hillsides created concerns for firefighters.
"The grass is tinder dry and there is a lack of humidity in the air," said Broschard. "The weather around here in September and October is cool in the morning and warm in the afternoon. It's the prime time for vegetation fires."
There was also a mild breeze and plenty of grass-covered hillsides for the fire to burn.
Todd Marsh, the general manager of nearby Club Sport, said his employees called in the fire as soon as they saw the flames above his facility.
He said firefighters acted quickly to get control of the fire.
"They put it out pretty quickly," he said.