While the number of wildfires and the total acres burned both declined in 2018 the average size continued to increase. The number of wildfires has been trending down since at least 1985 and the average size has been increasing. There are variations in the number of acres burned from year to year roughly in five to six-year cycles, but in the late 1980s the average size of a wildfire in the U.S. was 30 acres. That number has increased every decade since, bringing the average for this decade (to date) up to 101 acres.
The number of acres burned and the total number of fires decreased in 2018 from 2017 by 13 and 22 percent respectively, while the acres burned was sixth highest since records have been kept.
If the five to six-year cycle for burned acres that we noticed in the data is real, and continues, we could expect lower numbers for the next three to four years beginning in 2019 compared to 2017 and 2018.
The raw data we used to construct these charts is from the National Interagency Fire Center, current as of December 21, 2018. The historical data for Alaska before 1990 which we used to determine the numbers for the other 49 states is from a paper published by the University of Alaska.