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October wildfires like the Canyon Fire 2 in Anaheim Hills tend to burn more acres than those in any other month

October 9, 2017
A firefighter walks near a pool as a neighboring home burns in the Napa wine region in California on October 9, 2017, as multiple wind-driven fires continue to whip through the region.

The Canyon fire 2 burning in Anaheim hills has burned more than 2,000 acres and prompted evacuations of about 1,000 homes, destroying or damaging at least five homes.

If history is any indication, this fire could continue to grow.

According to analysis of 16 years of Calfire wildfire data, more acres burn per fire in California in October than in any other month.

While the June through September fire season generates more fires, in numbers, October fires are bigger. Between 2000 and 2015, October fires average 1,173 acres burned per year, while the average for the other four months is about 440 acres, according to Calfire data.

In the same time period between 2000 and 2015, the median acres burned for a wildfire in October was 1,711 while the number for July (the month with the most total fires) was 1,083.

Previous research has shown that a combination of heat and dry weather make the late summer and early fall months the most dangerous for fires. In a 2008 report by Dr. Anthony L. Westerling of UC Merced, he writes that 98 percent of acres burned in the Western U.S. happen between May and October.

“It should be reminded that, depending on location, most of the western U.S. is characterized by summer dryness … . Therefore, it is not surprising that the peak of the fire season occurs during the hottest and driest portion of the climatological annual cycle,” he writes in the report.

Five of the 20 largest fires in California between 2000 and 2015 have started in October.

 
  • The Cedar fire in San Diego County in October 2003 burned 273,000 acres.
  • The 2007 Witch fire, also in San Diego, burned nearly 198,000 acres.
  • The 2003 Simi fire in Ventura burned 108,000 acres.
  • The 2003 Old fire in San Bernardino burned 91,000 acres.
  • The 2007 Harris fire, again in San Diego, burned 90,000 acres.

While the overall trend for wildfires over the last 40 years has been decline, 2017 has been an outlier, generating several devastating fires statewide.

As of Sept. 11, Cal Fire had reported 5,102 wildland fires in their jurisdiction, fires that burned near 230,000 acres. During the same period of 2016, there were 3,803 wildfires and 204,000 acres burned. The five-year average has been 3,872 wildland fires and 155,807 acres burned, according to Calfire.

And as the fire raged in Orange County and threatened homes, the Wine Country wildfires north of San Francisco are building into the most destructive event in the state this year. At least 10 people have died, more than 100 are reported missing, more than than 1,500 structures have burned, and thousands of people have been forced to evacuate.

Huge fires tend to take time to contain. From 2000 to 2015, large wildfires (more than 300 acres burned) took nearly 10 days to contain on average. And the trend has been worsening. Between 2013 and 2015, the average days it took to contain large wildfires was nearly 15 days, according to Cal Fire data.