Does Smoke Happen Often in California?

Does Smoke Happen Often in California?

June 3, 2024 Blog Natural Disasters Weather 0

California is often beset by wildfires, especially during the hottest and driest months of the year, which is from May to October. In 2023, the California Department of Forestry and Fire Protection responded to more than 7,500 wildfire incidents. So how much smoke claims California?  A whole lot – over 500 wildfire incidents per month, on average!

Wildfires, of course, also mean smoke. In addition to carbon dioxide and other greenhouse gases, wildfire smoke also contains a mix of hazardous air pollutants, such as lead, ozone, PM2.5, NO2 and aromatic hydrocarbons. 

In addition, smoke contains a large amount of fine particle matter that can cause wheezing, coughing, and other respiratory, heart and lung diseases. Wildfire smoke can also exacerbate the effects of climate change, leading to hotter and drier summers and a decrease in winter snowpack. 

In California, how often wildfire smoke impacts people near and far depends on how many wildfires occur in a certain period and how long and intense these blazes burn. 

Wildfire Smoke Occurrences in California

Where there is fire, there’s sure to be smoke too. And, how large a fire can get also impacts how intense a smoke becomes as well. 

For instance, in 2020 and 2021, wildfire smoke covered as much as 70% of the state, according to a study from the University of California, Davis. In addition, the researchers found that the maximum smoke cover has also increased by 116,000 square miles since 2006. 

Furthermore, 2020 was the peak of potential population exposures to wildfire smoke, which have been increasing since 2010, according to the California Office of Environmental Health Hazard Assessment. The year 2020 also saw smoke plumes cover every county for 46 days minimum, whereas from 2010 to 2014, this was the case for only 11 counties. 

In terms of the largest wildfires, ergo the largest smokes, those that occurred in 2020 and 2021 top the charts. Majority of these fires also happened in the last decade or so, including the state’s largest wildfire seasons on record: 2018, 2020 and 2021. During these three years, researchers found an average of 33 days of high-density smoke between July and October. Only two wildfires from the 1990s were large enough to make it to the list below, one from 1932 when California started keeping official fire records.

The 20 Largest Wildfires in California
WildfireCounties AffectedMonth and YearAcres Burned
August ComplexMendocino, Humboldt, Trinity, Tehama, Glenn, Lake and Colusa countiesAugust 20201,032,648 acres
DixieButte, Plumas, Lassen, Shasta and Tehama countiesJuly 2021963,309 acres
Mendocino ComplexColusa, Lake, Mendocino and Glenn countiesJuly 2018459,123 acres
SCU Lightning ComplexStanislaus, Santa Clara, Alameda, Contra Costa and San Joaquin countiesAugust 2020396,625 acres
CreekFresno and Madera countiesSeptember 2020379,895 acres
LNU Lightning ComplexNapa, Solano, Sonoma, Yolo, Lake and ColusaAugust 2020363,220 acres
North ComplexButte, Plumas and Yuba countiesAugust 2020318,935 acres
ThomasVentura and Santa Barbara countiesDecember 2017281,893 acres
CedarSan Diego countyOctober 2003273,246 acres
RushLassen countyAugust 2012271,911 acres
RimTuolumne countyAugust 2013257,314 acres 
ZacaSanta Barbara countyJuly 2007240,207 acres
CarrShasta and Trinity countiesJuly 2018229,651 acres
MonumentTrinity countyJuly 2021223,124 acres
CaldorAlpine, Amador and El Dorado countiesAugust 2021221,835 acres
MatilijaVentura countySeptember 1932220,000 acres
River ComplexSiskiyou and Trinity countiesJuly 2021199,359 acres
WitchSan Diego countyOctober 2007197,990 acres 
Klamath Theater ComplexSiskiyou countyJune 2008192,038 acres
Marble ConeMonterey countyJuly 1977177,866 acres

Source: Western Fire Chiefs Association

Increasing Likelihood of Wildfires and Wildfire Smoke

Today, the state of California has an increased likelihood of wildfires (and wildfire smoke), thanks to climate change. These natural events have not only gotten more frequent but severe too.

Although California is not the state with the most wildfires, blazes can leave a devastating trail in the most populous state in the country. California has nearly 40 million residents, a great number of which live in houses located in the wildland urban interface (WUI). 

WUI is the transition zone between human development and unoccupied land. So, think wildland or vegetative fuels amidst houses and other structures, which significantly increases the likelihood of wildfires.

With such a close proximity between men and dry vegetation, it only takes a little spark to set the whole neighborhood ablaze. In fact, humans are the most common cause of wildfires. Based on an analysis of wildfire data, the U.S. Forest Service found that about 86% of wildfires in the state between 1992 and 2020 were ignited by human activity. Meanwhile, Cal Fires says the percentage is 95%. 

The most common causes of wildfires are arson, burning debris and blazes from equipment and vehicles. In addition to man-caused wildfires, the Los Angeles Times adds that the following also started wildfires in the state: lightning, signal fires, power lines or electrical equipment, and sparks from vehicles or lawnmowers.

The point is this: “We’re looking at a scenario where for the next 100 years or longer, smoke will be a feature on the landscape,” senior author Steven Sadro, an associate professor in environmental science at the University of California, Davis, said in a statement.

And, some counties are more at risk for wildfires (and wildfire smoke) than others. According to the Federal Emergency Management Agency (FEMA), these counties are as follows: 

CountyRisk IndexOverall rating of wildfire risksFrequency
Riverside CountyVery high100%2.4% chance per year
San Diego CountyVery high100%2.7% chance per year 
San Bernardino CountyVery high99.9%0.97% chance per year
Los Angeles CountyVery high99.9%0.8% chance per year
Ventura CountyRelatively high99.8%1.3% chance per year
Orange CountyRelatively high99.8%1.5% chance per year
Kern CountyRelatively high99.7%0.7% chance per year
Madera CountyRelatively high99.6%0.8% chance per year
Santa Barbara CountyRelatively high99.5% 0.8% chance per year
Tuolumne CountyRelatively high99.5%0.96% chance per year
Calaveras CountyRelatively high99.4%0.9% chance per year

Source: GovTech