The U.S. is on track to shatter the record for the average size of wildfires this year

Bill Gabbert
December 3, 2020

Average wildfire size in the United States 1985-2020 — Average wildfire size in the United States, except Alaska, 1985-2020.

While all the wildfire statistics for 2020 are not yet available, the data through December 2, 2020 shows that the United States is on track to shatter the record for the average size of wildfires. Looking at the last 35 years, the average size of fires this year was the highest ever, 168 acres. This number has been growing rapidly year to year (see the chart above). The second highest was 145 acres in 2018, and third highest was 132 in 2017.

From 1985 through 1993 the average size was 27 acres — 16 percent of the average size in 2020, 168 acres.

Total wildfire acres US 1985-2020 — Total wildfire acres US except Alaska, 1985-2020

Number of wildfires US 1985-2020 — Number of wildfires US except Alaska, 1985-2020

From looking at the data, here are some highlights:

During the last 35 years, the number of acres burned this year in the lower 49 states was the 5th highest.
The number of fires has been declining. This year was the fourth lowest number in the last 35 years. The first, second and third lowest were 2013, 1989, and 2019 respectively.

Fewer, but larger fires — why?

The number of fires may be declining because we are better at preventing them. NFPA data shows the number of highway vehicle fires has declined from 456,000 in 1980 to 182,000 in 2018. The highway vehicles fires per billion miles driven has decreased over that same period from 299 to 56. In addition, we may have better spark arrestors on equipment, and, fewer people are smoking and those that do, smoke less.

Higher temperatures most likely has led to lower live and dead fuel moistures, more preheating of vegetation, extreme weather, more rapid fire spread, and increased resistance to control of fires. And when there is more fire on the landscape, the same number of forestry technicians year after year can’t suddenly increase their firefighting output by 300 percent.

All of the wildfire data in our charts here excludes Alaska. I treat that state separately because:

They don’t fully suppress most fires in Alaska, or sometimes just try to herd them away from communities. Fires can grow huge which really skews the numbers for the nation.
Alaska’s burned acres can vary widely from year to year. For example, so far this year they have only burned 181,234 acres; the other 49 states burned 8,708,060. In 2015 5,111,404 acres burned in Alaska.

I also do not show on charts the numbers before 1985 because the data available from NIFC shows wide shifts between 1982 and 1984. It appears that a different record-keeping system was introduced at that time.