The indicators are subtle: lower than average rainfall, lower than average moisture content in grasses and brush, lower than average snow accumulation in the Sierras.
They add up to a higher than average danger of wildfire for the 2012 fire season, which began in mid-May and which is a special concern for forested communities such as Woodside and Portola Valley, said Fire Chief Dan Ghiorso of the Woodside Fire Protection District.
Firefighters from the district will be alerting the community between now and November on days when the danger is particularly high. White signs with red letters will go up in key locations visible from the road, he said.
The dry conditions this year have occurred five times over the last 40 years, and each time the number of wildfires was unusually high, Chief Ghiorso said.
The first five months of 2012 saw 1,577 fires, nearly twice as many as the 847 in 2011, according to the website of the California Department of Forestry Fire Protection. This year's count also exceeds the five-year average of 1,307 fires over those five months.
In exceptionally dry conditions, Cal Fire boosts its firefighting staff and redeploys its firefighting aircraft to strategic locations around the state.
"It only takes one little spark to ignite a wildfire," says a warning on Cal Fire's website.
The Woodside fire district is encouraging residents to participate in the annual summer brush chipper program.