Kelseyville firefighters prepare to pull back from the fire on Butts Canyon Road, as the fire jumps the road, Tuesday July, 1, 2014, outside Middletown, Calif., at the border between Lake and Napa counties. By early evening 140 homes were evacuated and 2,500 acres were burned. (AP Photo/The Press Democrat, Kent Porter)

Here’s a most surprising statistic: Western wildfire activity – thus far this summer  – is the lowest in at least 10 years.

The number of acres burned is just 38 percent of average.

“Comparing acres burned through Aug. 4 for each of the past 10 years, 2014 is well below the norm, with just 1.7 million acres burned to date,” writes the Daily Climate. “The average for the other nine years is 4.4 million, according to the National Interagency Fire Center.”

(Data via National Interagency Fire Center)

This is not at all what wildfire experts predicted. And it’s incredibly counter-intuitive.

The West is unmistakably hot and dry.  California is having its hottest year on record and temperatures in most western states are running above to much above normal.

Temperature rankings compared to normal for the Lower 48 January-June (NOAA)

And, of course, the western drought is devastating and keeps getting worse.

U.S. Drought Monitor, July 31, 2014.

The pre-season wildfire forecast, issued in April by the National Interagency Fire Center, called for above normal wildfire activity in much of California and the Southwest.  The forecast assumed the heat and expanding drought would dry out the land surface, creating tinderbox conditions.

Wildfire forecast for June and July issued April 1 (National Interagency Fire Center)
Wildfire forecast for June and July issued April 1 (National Interagency Fire Center)

In reality, wildfire activity has been close to normal in these areas.

In California, for example, 34,576 acres had burned through July 26, not far off the 5-year average of 40,236 acres and well below 2013’s 67,980 acres at the same time.

The northern Rockies have had a particularly quiet wildfire season (this was predicted as a result of substantial winter snowpack).

So why hasn’t there been more action?

In  parts of the West, fires have lacked a trigger according to Steve Running, a wildfire expert at the University of Montana.

“Wildfires need dry fuels AND an ignition source,” Running said in an email. “Our western wildfires are mostly lightning ignited, so if there are no lightning storms we can go a long time with high fire vulnerability, but few actual fires.”

Could it be the drought – though desiccating – is limiting the opportunities for thunderstorms that would set off the fires? “That’s a stretch,” Running said. “It is more likely just pure probability that a lot of lightning storms have not occurred over dry forests.”

While wildfire activity has been relatively scarce so far, the season continues through the fall and the amount of combustible material is extremely high in California and the Southwest. Wildfire activity could still explode.

“The fire season is far from over,” Max Moritz, a wildfire expert at the University of California at Berkeley, said in an email. “For example, southern Cali. shrublands — where so much of the population has settled — typically has its worst fire activity later in the Sept-Oct fall months.  Furthermore, moisture content of both dead and live vegetation is so low in many western regions… whether the season gets bad kind of hinges on whether we have any extreme wind events that happen to coincide with an ignition.  The potential for that to happen between now and the (hoped for) rainy season is still quite high.”

The relatively slow fire season runs counter to recent trends.  Western wildfire activity has increased substantially over the past decade compared to the 1970s and 1980s.  From a 2012 Climate Central report on western wildfires:

Our analysis of 42 years of U.S. Forest Service records for 11 Western states shows that:

The number of large and very large fires on Forest Service land is increasing dramatically.  Compared to the average year in the 1970’s, in the past decade there were:

* 7 times more fires greater than 10,000 acres each year

* Nearly 5 times more fires larger than 25,000 acres each year

* Twice as many fires over 1,000 acres each year, with an average of more than 100 per year from 2002 through 2011, compared with less than 50 during the 1970’s.

(Climate Central)

A number of factors, including rising temperatures, declining snowpack and forest management practices, have led to the uptick, explained Climate Central’s Andrew Freedman (now at Mashable):

Many factors are involved in creating conditions that are primed for large wildfires. In addition to warming temperatures and changing snowpack trends, decades of fire suppression strategies have left large tracts of forest with excess fuel to burn. Increased human development near traditionally fire-prone ecosystems has contributed to an uptick in damaging fires, and natural climate and weather variability plays a large role as well.

The 2014 National Climate Assessment expects wildfires to increase in the coming decades given projected warming: “In some regions, prolonged periods of high temperatures associated with droughts  contribute to conditions that lead to larger wildfires and longer fire season.”

(Angela Fritz contributed to this post.)