These California counties have the highest share of homes vulnerable to wildfire

Deadly wildfires, once again, have pushed the conversation about the risk of living in some parts of California to the forefront. A new analysis by insurance data provider Verisk Analytics shows that more people are in danger than you might think.

More than 2 million homes - about 15 percent of all housing units in the state - have high to extreme risk of wildfire damage, according to the New Jersey-based firm. In seven counties, mostly in Northern California, more than two-thirds of all homes were in jeopardy.

Verisk Analytics used three factors to determine risk, including how close a property is to forests, shrubs and trees; whether it is near hilly or mountainous terrain; and if it is hard to reach and isolated. More than 500,000 acres burned last year which included the Tubbs fire in Sonoma County that eliminated more than 5,600 structures and took 22 lives.

The Verisk analysis showed that Alpine, Trinity, Tuolumne, Mariposa and Nevada counties had the highest concentration of houses at risk, according to the analysis. Meanwhile, Los Angeles, San Diego, San Bernardino, Ventura and Alameda counties had the largest number of units at risk.

In the case of the northern counties, the risk will be higher because homes there often dispersed at the edge of a wildland area, said Lenya Quinn-Davidson, a Eureka-based fire advisor for the University of California Division of Agriculture and Natural Resources.

“Those areas that you mentioned are areas that have a lot of homes mixed into the wildland-urban interface - areas where there are a lot of homes that are edgy and in the forest and have a lot of fuel.”

Quinn-Davidson said many homes actually burn not from the front of the fire but from embers landing on roofs filled with debris or nearby shrubs.

“And if you get an ember landing on your rain gutters and your rain gutters are packed with leaves that's a sure way to have your house burn down,” Quinn-Davidson said. “That's how we're losing these homes. It's not from the fire actually burning over the house.”