California Experiencing 85% Increase in Wildfire Smoke Waves, Study Finds

As California faces an increasing frequency of wildfires, communities across the state are getting significantly less time to recover from wildfire smoke, according to a new study.

The spatio-temporal analysis, published in GeoHealth journal, examined shorter recovery periods between smoke events and defined the “recovery period” as the time between smoke waves in California from 2006 to 2020.

Researchers defined a smoke wave as two or more consecutive days with wildfire-specific fine particulate matter (PM2.5) greater than 1 microgram per cubic meter. 

The study found that recovery periods have shrunk by about 60%, while the number of smoke events has increased by roughly 85%.

The frequency of smaller fires has increased by nearly 200% from the late 1920s to the late 2010s, with climate change, land management decisions, and human pressures worsening wildfire extremes.

According to the study, shorter recovery periods mean that communities have less time between smoke episodes, potentially compounding the risk of repeated exposure and health impacts. 

Wildfire smoke exposure patterns have changed significantly across the state in the last decade and a half, according to the study.

The average recovery period between smoke events fell from about 208.8 days in 2006-2010 to 76.3 days in 2016-2020.

Regional and Community Differences

The study found that wildfire smoke patterns vary across different regions of the state. 

Northern California, which already had the shortest recovery periods, showed minimal changes. 

However, smoke wave events increased across California in 2020, when census tracts recorded an average of nearly 46 smoke-wave days that year.

In contrast, Southern and Central California saw the largest reductions in recovery periods, indicating a rapid change toward more frequent smoke exposure in these regions. 

The study also examined how recovery periods changed across different community characteristics.

Census tracts with higher proportions of minority racial groups, lower household incomes, and more single female-led households experienced the largest reductions in recovery time between smoke waves.

On the other hand, areas with larger populations of White residents, multiracial residents, and older adults generally saw smaller decreases, or even increases, in recovery periods. Many of these tracts were located in the Sierra Nevada and Northern California regions, which frequently experienced wildfire smoke waves.

A 2025 study published in Nature found that climate-driven wildfire smoke deaths could result in economic damages that exceed existing estimates of climate-related damages from other causes combined in the U.S.

Smoke-related PM2.5 exposure could result in more than 71,000 excess deaths per year by 2050 under a high-warming scenario, which is about a 73% increase compared with the estimated 2011–2020 annual average, according to the study.