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Why the devastating California wildfires have been so unusual, extreme this December

By Amanda Schmidt, AccuWeather staff writer
December 22, 2017, 9:50:10 PM EST

Several large and devastating wildfires have led to mass evacuations in Southern California this December, which is extremely unusual for this time of year.

Most notably, the Thomas Fire, which has burned 273,400 acres, has become the largest wildfire in California history. This is larger than the Cedar Fire, which burned 273,246 acres in October 2003 in San Diego, according to CalFire.

While this December has been particularly active, the month typically tends to be one of the calmer months in terms of wildfires.

There have been only eight California wildfires that burned more than 300 acres in December from 2000 to 2015. The second lowest months for large fire activity are January and February, according to CalFire.

In comparison, there have already been six wildfires that burned more than 300 acres this December.

CA wildfire 12-14-17

In this Thursday, Dec. 14, 2017, photo provided by the Santa Barbara County Fire Department, flames from a back firing operation underway rise behind a home off Ladera Lane near Bella Vista Drive in Santa Barbara, Calif. (Mike Eliason/Santa Barbara County Fire Department via AP)

Of the eight fires in December from 2000 to 2015, five were in Southern California and two were in Ventura County.

The total acres burned in those seven fires is 22,835, which is only a fraction of the Thomas Fire burning in Ventura County.

The previous largest fire in December was the Shekell Fire in Ventura, which burned 13,600 acres in 2006.

Wildfires are rare in December due to typical weather patterns in the Golden State. California has a dry season and a rainy season. The wet season typically peaks between December and March.

Extreme wildfires do not usually happen in California during December because it is usually in the wet season, according to AccuWeather Meteorologist Jordan Root.

“Storms usually start to dip farther south across the western United States late in the year, which brings rain and mountain snow to the state,” Root said.

However, this year has been different. There are two main factors that are contributing to the extreme wildfires this December.

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The year started out historically wet across the state, causing an abundance of new vegetation. This vegetation dried out during the hot and dry summer season.

“This has provided more dry fuels than normal,” Root said.

Areas outside of Northern California have not seen much, if any, rain so far during the early part of the wet season.

“With Santa Ana wind events usually peaking late in the year, the combination of this, new vegetation from earlier in the year and the dry start to the rainy season have all led to dangerous fire conditions extending into December,” Root said.

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