Insured losses from the California wildfires are now more than $1 billion according to a leading industry analyst.

The extent of destruction to insured property caused by at least 16 significant wildland fires burning across the state from Santa Barbara to San Diego now equates to a one-in-eight years event.

And the evacuation of half-a-million residents is the biggest such forced evacuation in the US since Hurricane Katrina battered New Orleans in 2005.

EQECAT, which provides state-of-the-art risk management software to the insurance industry, estimates that insured losses to date from the California fires have exceeded $1 billion, with the expectation the losses will continue to grow until the winds die down and firefighters are able to contain the fire.

In a statement the company said: "The fires are being driven by the 'Santa Ana' wind conditions. These winds are a 'foehn wind' - high speed winds spilling out of the central western US, heated and dried by the Mojave Desert, and concentrated and channeled into the Los Angeles basin.

"These wind conditions occur throughout the year, with about 2-3 days of these conditions per quarter. All of the major California brush fires (fires with extents greater than 10,000 acres) have been accompanied by these wind conditions. Exacerbating these wind conditions are an unusually dry preceding winter and (normal) dry summer."

EQECAT has a wildland brushfire model that produces an expectation of a billion-dollar fire loss every eight years and a $2 billion insurance industry wildfire loss every 15 years.

"From this perspective, this year's fires are extreme but not unusually so. California is a large state with a significant proportion of unpopulated wildland areas and accompanying fire risk. Accompanying this is the trend of the last several decades of populating the 'wildland-urban' interface area, exposing more people and insured values to the ever present fire risk in California," said EQECAT.

"Wildland-urban fire losses tend to be concentrated in the personal lines sector of the market. The losses tend to be in newer neighborhoods, but given this the demographics of the burnt areas are quite varied, ranging from newer subdivisions to elite homes."

There were dramatic fire seasons in 2003, when more than 3,600 dwellings burnt, and 1993.