Background on: Wildfires


Fire plays an important role in the life of a forest, clearing away dead wood and undergrowth to make way for younger trees. But for much of the last century, fire-suppression policies have sought to extinguish wildfires as quickly as possible to preserve timber and real estate. This approach has led to the accumulation of brush and other vegetation that is easily ignited and serves as fuel for wildfires.

Most of the large fires with significant property damage have occurred in California, where some of the fastest developing counties are in forest areas that were once largely uninhabited. These areas, known as the Wildland-Urban Interface (WUI), contained about a third of all housing units in the United States in 2017, according to the U.S. Forest Service. Fast-growing areas with moderate to high wildland fire potential range from parts of the South to large parts of the West. Rising temperatures and more intense droughts are also believed to contribute to large, destructive blazes. Warmer weather contributes to wildfire conditions in many ways: dryer and more combustible vegetation, more frequent lightning strikes, an extended fire season, more intense winds and earlier spring snowmelt in mountainous areas leading to dry vegetation earlier in the wildfire season. A typical wildfire season would run from mid-summer to early autumn, but with these changing conditions wildfires are becoming a year-round occurrence.

Insured wildfire losses

Damage caused by fire and smoke are covered under standard homeowners, renters and business owners insurance policies and under the comprehensive portion of an auto insurance policy. Water or other damage caused by fire fighters to extinguish the fire is also covered under these policies. In California, the California FAIR Plan covers residential and commercial properties located in brush and wildfire areas. Properties in those areas are subject to higher rates due to increased risk of fire

Causes of wildfires

As many as 90 percent of wildland fires in the United States are caused by humans, according to the U.S. Department of Interior. Some human-caused fires result from campfires left unattended, the burning of debris, downed power lines, negligently discarded cigarettes and intentional acts of arson. The remaining 10 percent are started by lightning or lava.

Wildfire prevention and mitigation

Researchers are discovering that embers blown by the wind during wildfires cause most of the fires that burn homes. Also, homes that are less than 15 feet apart are more likely to burn in clusters. In such cases, fire is often spread by combustible fences and decks connected to houses, a study by the Insurance Institute for Business & Home Safety (IBHS) found.

Among the preventive features recommended in the IBHS study were noncombustible siding, decking and roofing materials; covered vents; and fences not connected directly to the house. In addition, combustible structures in the yard such as playground equipment should be at least 30 feet away from the house and vegetation 100 feet away.

Properties at risk for wildfires

FireLine®, Verisk’s wildfire risk management tool, assesses wildfire risk at the address level using advanced remote sensing and digital mapping technology. The three primary factors considered in analyzing wildfire risk are distribution of vegetative fuel, steepness of slope and degree of access for firefighting equipment. FireLine assigns a wildfire hazard score for each factor plus a cumulative score, on a scale from negligible to extreme risk. The following chart ranks the most wildfire-prone western U.S. states by high to extreme wildfire risk as of 2019. According to Verisk estimates, more than 4.5 million U.S. properties are at high to extreme wildfire risk, with more than 2 million in California alone.

Charts and graphs

Top 10 States At High To Extreme Wildfire Risk, 2019 (1)


Rank State Estimated number
of properties at risk
Rank State Percent of
properties at risk
1 California 2,019,800 1 Montana 29%
2 Texas 717,800 2 Idaho 26
3 Colorado 371,100 3 Colorado 17
4 Arizona 237,900 4 California 15
5 Idaho 175,000 5 New Mexico 15
6 Washington 160,500 6 Utah 14
7 Oklahoma 153,400 7 Wyoming 14
8 Oregon 151,400 8 Oklahoma 9
9 Montana 137,800 9 Oregon 9
10 Utah 136,000 10 Arizona 8

(1) As of September 2019.

Source: Verisk Wildfire Risk Analytics used data from FireLine®, Verisk's wildfire risk management tool.

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Wildfire Lossses In The United States, 2010-2019 (1)

(2019 $ millions)

(1) Adjusted for inflation by Munich Re based on the Consumer Price Index.

Source: © 2020 Munich Re, NatCatSERVICE.

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Natural Catastrophe Losses In The United States, 2019 (1)

($ millions)

Event Number of events (2) Fatalities Overall losses Insured losses (3)
Severe thunderstorm 49 70 $27,000 $20,300
Winter storms and cold waves 16 73 7,400 2,100
Tropical cyclone 5 16 3,900 1,900
Wildfire, heat waves, and drought 9 11 1,300 830
Flood, flash flood 9 7 10100 200
Earthquake and geopyhsical 2 3 180 50
Total 90 180 $49,900 $25,500

(1) As of May, 2020.
(2) Events that have caused at least one fatality or losses of $3 million or more.
(3) Sourced from Property Claim Services based on property losses including, if applicable, agricultural, offshore, marine, aviation and National Flood Insurance Progam losses; may differ from data shown elsewhere.

Source: © 2020 Munich Re, NatCatSERVICE, Property Claim Services®, a unit of ISO®, a Verisk Analytics® business.

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Top 10 States For Wildfires Ranked By Number Of Fires And By Number Of Acres Burned, 2019


Rank State Number of fires Rank State Number of acres burned
1 California 8,194 1 Alaska 2,498,159
2 Texas 6,892 2 Arizona 384,942
3 North Carolina 3,872 3 Idaho 284,026
4 Georgia 3,158 4 California 259,148
5 Oregon 2,293 5 Texas 215,493
6 Florida 2,121 6 Washington 169,742
7 Arizona 1,869 7 Florida 122,500
8 Montana 1,474 8 Utah 92,380
9 Washington 1,394 9 Nevada 82,282
10 Alabama 1,107 10 New Mexico 79,887

Source: National Interagency Fire Center.

View Archived Tables

Top 10 Costliest Wildland Fires In The United States (1)

($ millions)

      Estimated insured loss
Rank Date Name, Location Dollars when
In 2019
dollars (2)
1 Nov. 8-25, 2018 Camp Fire, CA (3) $8,500-$10,500 $8,700-$10,700
2 Oct. 8-20, 2017 Tubbs Fire, CA (3) 7,500-9,700 7,800-10,100
3 Nov. 8-22, 2018 Woolsey Fire, CA (3) 3,000-5,000 3,100-5,100
4 Oct. 8-20, 2017 Atlas Fire, CA (3) 2,500-4,500 2,600-4,700
5 Dec 4-23, 2017 Thomas Fire, CA (3) 1,500-3,500 1,600-3,600
6 Oct. 20-21, 1991 Oakland Hills Fire, CA 1,700 2,900
7 Oct. 21-24, 2007 Witch Fire, CA 1,300 1,600
8 Jul. 23-Aug. 30, 2018 Carr Fire, CA (3) 1,000-1,500 1,000-1,500
9 Oct. 25-Nov. 4, 2003 Cedar Fire, CA 1,060 1,400
10 Oct. 25-Nov. 3, 2003 Old Fire, CA 975 1,300

(1) Property losses only for catastrophic fires. Effective January 1, 1997, ISO's Property Claim Services (PCS) unit defines catastrophes as events that cause more than $25 million in insured property damage and that affect a significant number of insureds and insurers. From 1982 to 1996, PCS used a $5 million threshold in defining catastrophes. Ranked on dollars when occurred. As of September 30, 2020.
(2) Adjusted for inflation through 2019 by the Insurance Information Institute using the GDP implicit price deflator.
(3) Insurance Information Institute estimate based on data from catastrophe risk modelers, reinsurance companies, the California Department of Insurance, and the Property Claims Services unit of Verisk Analytics. These estimates are preliminary because the organizations involved periodically resurvey the events, and the severity of losses and other factors create a high level of uncertainty surrounding the ultimate loss figures.

Source: Insurance Information Institute, catastrophe risk modelers, reinsurance companies, the California Department of Insurance, the Property Claim Services® (PCS®) unit of ISO®, a Verisk Analytics® company, and the U.S. Bureau of Economic Analysis.

View Archived Tables

Additional resources

Verisk Insurance Solutions' FireLine State Risk Report

National Interagency Fire Center

Headwaters Economics - The Rising Cost of Wildfire Protection

Insurance Institute for Business & Home Safety – Wildfire resources

National Fire Prevention Administration - Wildfire safety tips

Wildfire Hazard Potential Map

Cal Fire's

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