On September 9, 2020, San Francisco’s midday sky turned orange. Smoke from fires burning hours north had settled over the Bay Area so completely that no direct sunlight reached the city. The fires themselves were nowhere near San Francisco. That’s the part worth remembering.
This San Francisco wildfire and smoke map tracks where fires are burning right now: active perimeters, smoke drift, and air quality readings across the Bay Area, pulled from CAL FIRE, AirNow, and the USFS Active Fire Mapping Program. It updates continuously during active fire conditions. If you’re looking for where the fire is, start with the map. The rest of this page gives you the context to understand what you’re seeing and what to do about it.
TL;DR Quick Answers
- This map shows live fire locations, smoke drift layers, and AQI readings for the San Francisco Bay Area.
- Data comes from CAL FIRE, AirNow, and the USFS, updated in real time during active fire conditions.
- If AQI exceeds 150, stay indoors, limit outdoor activity, and run a HEPA filter for home air purifier if you have one. Making sure your HVAC filter is also rated MERV 13 or higher is the parallel step that protects every room the purifier doesn’t reach.
- For active evacuation orders, go directly to AlertSF or the Cal OES Ready for Wildfire site.
- Wildfire season in California peaks from June through November, but fires now occur year-round, including during winter wind events.
- An N95 or P100 respirator is the only face covering that meaningfully filters wildfire smoke particles outdoors.
Top Takeaways
- San Francisco is particularly exposed to smoke from fires far inland, especially during Diablo Wind and Delta Breeze conditions that push smoke directly toward the coast. Checking Oakland air quality right now gives Bay Area residents a near-real-time read on whether smoke has already crossed the bay and is heading toward SF.
- The 2018 Camp Fire burned over 150 miles north of San Francisco and still pushed AQI readings into hazardous territory for nearly two weeks. Distance doesn’t equal safety. The same long-range transport that pushes smoke drifting toward Pennsylvania from distant fires applies to every city downwind of a major burn, including SF.
- Wildfire smoke contains PM2.5, fine particulate matter small enough to bypass the nose and throat and settle deep in lung tissue. Short exposures at high AQI can affect otherwise healthy adults.
- AQI below 100 is generally acceptable for healthy adults. Above 150, everyone should reduce outdoor exposure, not just sensitive groups.
- Air quality can shift dramatically in under an hour when wind changes during an active fire event. If you’re planning time outside, check the map more than once.
- A cloth mask or surgical mask filters almost no PM2.5. Only an N95 or P100 respirator, fitted properly with no gaps, offers real protection.
Table of Contents
What This Map Shows and How to Use It
Three data layers are running on this map at once: active fire perimeters, smoke plume density, and Air Quality Index readings by location. CAL FIRE and the USFS Active Fire Mapping Service supply the fire perimeter data, drawing from satellite detection and ground crew incident reports. Smoke layers come from NOAA’s dispersion forecasts, which model where plumes move based on wind speed, direction, and atmospheric conditions. AQI readings pull from EPA monitoring stations and community sensors on the PurpleAir network.
To read it: zoom into your neighborhood and find the AQI reading closest to you. Fire perimeters show as colored boundary lines around active incidents. The smoke density overlay helps you decide whether to open windows or keep them closed — and whether your home air filters are rated for what’s coming in. The map legend explains what each color means. When conditions are shifting fast, refresh the page. Real-time data goes stale quickly during an active fire.
One thing to keep in mind: fire perimeters reflect the last boundary reported by incident command, which can lag several hours behind a fast-moving fire. Use perimeter data for orientation, not precision. For evacuation decisions, defer to official orders from AlertSF, your county’s Office of Emergency Services, or Cal OES.
Why San Francisco Gets Hit by Smoke From Fires Far Away
California’s interior burns hard during fire season. The foothills, the Sierra Nevada, the Central Valley — when those areas ignite, the Bay Area’s prevailing winds regularly carry smoke westward toward the coast. Two wind patterns make this worse. Diablo Winds blow hot and dry from the northeast in autumn, driving some of California’s most destructive fires while pushing smoke directly into the Bay. Delta Breeze, the marine airflow that normally cools the Bay Area, can reverse during inland heating events and channel smoke onshore rather than dispersing it.
A fire burning 100, 150, even 250 miles away can produce days of unhealthy air in San Francisco. The 2018 Camp Fire near Paradise killed 85 people and became the deadliest wildfire in California history. It also sent smoke thick enough to block the sun over the Bay Area for close to two weeks. The 2020 fire season burned over four million acres statewide and produced weeks of some of the worst recorded air quality the region has seen. Checking your AC filter sizes and upgrading to MERV 13 before smoke season is the preparation step most Bay Area households skip until it’s too late to order.
Fire behavior follows a specific logic of topography, fuel, and wind — which explains directly why smoke patterns are so difficult to predict beyond a few hours out. Wikipedia’s overview of wildfires covers that science clearly for anyone who wants to understand what drives the spread.
What to Do When Smoke Reaches San Francisco
Start with your number. AQI readings vary by 50 to 100 points across the Bay Area when smoke is patchy. A regional average won’t tell you what’s happening on your block. Check AirNow.gov or the PurpleAir map for a reading specific to your zip code before making any outdoor plans.
At AQI 51 to 100, air quality is acceptable for most people, though unusually sensitive individuals may want to limit prolonged outdoor exertion. At 101 to 150, people with asthma, heart disease, or lung conditions, along with children and older adults, should limit time outside. At 151 and above, that applies to everyone: stay indoors, close windows and doors, and run a HEPA air purifier if you have one. Understanding what MERV 11 actually filters out of your air helps clarify why upgrading beyond the default MERV 8 makes a measurable difference at this AQI level. For those who care about where their filter comes from, why filter quality and domestic manufacturing matter is worth reading before you buy. If you don’t have a replacement on hand, finding replacement HVAC air filters near me can save critical time during an active advisory.
At 200 and above, stop outdoor activity. At 300 and above, indoor air quality becomes a serious concern too. Run your furnace air filters on recirculation with MERV 13 or higher, and seal any visible gaps around doors and windows.
If you must go outside during a smoke event, wear an N95 or P100 respirator that sits flat against your face with no gaps at the nose or chin. A cloth mask, gaiter, or surgical mask filters almost no PM2.5. It’s not a substitute. If the choice is going outside unprotected or staying in, stay in.
“Having monitored Bay Area air quality through multiple fire seasons, the most consistent mistake I see is people relying on regional AQI averages when smoke is patchy — your neighborhood sensor can be telling a completely different story than the city-wide number, and that gap matters when you’re deciding whether to keep the windows open or let your kids play outside. The single most reliable habit is to check a hyper-local sensor within half a mile of your home before making any outdoor decision during an active smoke event.”
7 Essential Resources
1. Wildfire
If you want to understand why smoke from a fire in Butte County reaches San Francisco within hours, this is the place to start. Wikipedia’s wildfire article covers how fires ignite and spread, the role of wind and topography in fire behavior, and a global record of major fire events. The sections on fire weather and smoke dispersal are particularly useful for Bay Area residents trying to make sense of air quality patterns during distant fire events. The entry draws from peer-reviewed research and updates regularly as new incidents and science emerge.
Source: Wikipedia
2. CAL FIRE Incident Information
CAL FIRE oversees fire protection across 31 million acres of California’s privately-owned wildlands. During active fire events, its incident information page updates continuously with fire names, acreage burned, containment percentages, and locations across the state. For tracking fires that may affect Bay Area air quality, this is the right source — not social media, not news aggregators. CAL FIRE also publishes post-season totals on fires, acreage, and structures lost, giving useful historical context to California’s long-term wildfire picture.
Source: CAL FIRE
3. AirNow
AirNow is the EPA’s real-time air quality platform, pulling data from thousands of monitoring stations across the country into a single searchable map. Enter a zip code and you get current AQI, the dominant pollutant, and a plain-language health guidance statement. During wildfire events, the platform separates routine air quality readings from smoke-specific events. It also hosts a dedicated Fire and Smoke Map that overlays active fire locations with smoke density and air quality readings in one view.
Source: AirNow — U.S. Environmental Protection Agency
4. AlertSF
AlertSF is San Francisco’s official emergency notification system. Sign up and you receive text, email, or phone alerts for wildfires, earthquakes, flooding, and public health advisories. During an active fire or smoke event affecting the city, AlertSF carries official guidance, shelter-in-place advisories, and evacuation orders. Signing up is free and takes under two minutes — one of the most concrete things any SF resident can do to stay ahead of a fast-moving situation.
Source: AlertSF — San Francisco Department of Emergency Management
5. Ready for Wildfire
Cal OES runs this preparedness platform to help California residents get ready before fire season arrives. The most practical feature is an address-level evacuation zone lookup that shows your property’s risk designation and explains what an evacuation warning versus an evacuation order actually means. The site also covers household preparedness checklists, defensible space guidance, and real-time links to active incident information during emergencies. Knowing your evacuation zone before a fire starts is a different experience than discovering it while one is moving.
Source: Ready for Wildfire — California Governor’s Office of Emergency Services
6. Community Air Quality Network
PurpleAir runs a global network of community-owned air quality sensors that report PM2.5 readings in near real time. AirNow draws from regulatory-grade monitoring stations that are highly accurate but spread thin across most neighborhoods. PurpleAir fills those gaps with block-level data that reveals pockets of poor air quality that broader maps miss entirely. The platform applies a correction factor to its readings to align more closely with regulatory-grade measurements, and its map updates every few minutes during active conditions.
Source: PurpleAir
7. National Oceanic and Atmospheric Administration
NOAA’s National Weather Service issues fire weather watches and red flag warnings during California’s fire season. A Red Flag Warning signals that high winds, low humidity, and dry fuels have aligned in a way that makes fire ignition and rapid spread highly likely. For Bay Area residents, these warnings typically arrive just before the most dangerous periods for smoke events. NOAA also publishes smoke dispersion forecast maps showing where plumes are expected to travel over the next 24 to 48 hours, based on current atmospheric conditions.
Source: NOAA National Weather Service
3 Statistics
1. California’s 2020 Fire Season: More Than 4.2 Million Acres Burned
California’s 2020 wildfire season burned approximately 4.2 million acres, the largest single-season total in the state’s modern recorded history. That’s more than four percent of California’s entire land area consumed in one year. For the Bay Area, 2020 produced the orange skies of September 9, when smoke sat so thick at elevation that virtually no direct sunlight reached the city. Midday looked like dusk. The scale of that season is why Bay Area air quality can’t be read independently of what’s burning across the broader state.
Source: CAL FIRE — Stats and Events
2. PM2.5 Above 35.4 μg/m³ Triggers “Unhealthy for Sensitive Groups” Status
The EPA’s AQI crosses into “Unhealthy for Sensitive Groups” territory when the 24-hour average PM2.5 concentration reaches 35.4 micrograms per cubic meter, corresponding to an AQI of 101. At 55.4 μg/m³ (AQI 151), the classification becomes “Unhealthy” for everyone. During the worst Bay Area smoke events in recent years, 24-hour PM2.5 averages at some monitoring stations exceeded 100 μg/m³, close to three times the threshold that triggers general health warnings. At those levels, even brief outdoor exposure carries measurable respiratory risk for healthy adults.
Source: U.S. Environmental Protection Agency — AQI Basics
3. Western U.S. Wildfire Season Is Now Two to Three Months Longer Than in the 1970s
NOAA’s National Centers for Environmental Information data shows the average wildfire season in the western United States has extended by roughly two to three months compared to the 1970s and 1980s. Earlier snowmelt, prolonged summer drought, and rising temperatures have pushed fire risk outside what was once a well-defined seasonal window. Parts of California now see fire weather conditions year-round. For Bay Area residents, the window during which a distant fire can affect local air quality is no longer June through October — it’s any month.
Source: NOAA Climate.gov
Final Thoughts and Opinion
We’ve covered Bay Area air quality and wildfire risk long enough to notice a consistent pattern. Every time smoke rolls in, the same confusion follows: one app shows AQI at 80, another shows 140, the sky outside looks almost clear, and nobody agrees on whether to cancel outdoor plans or just crack a window. This isn’t a failure of information. It’s a failure of hyperlocality — most people check regional averages when the reading two blocks away tells a different story.
Wildfire smoke is a year-round reality for San Francisco now. The data from ten-plus fire seasons confirms it, and the trend points one direction. Having a MERV 8 pleated furnace filter on hand as a baseline and a MERV 13 as your smoke-season upgrade means you’re never running a spent filter when the air matters most. For homes with 2-inch slots, a MERV 8 pleated HVAC filter 4-pack in the correct depth covers the season.
The most useful thing you can do before smoke arrives is spend 30 minutes building the habit. Find your nearest PurpleAir sensor. Look up your evacuation zone at readyforwildfire.org. Sign up for AlertSF. Put an N95 somewhere you’ll actually find it. None of that is hard to do today. All of it is much harder when you’re squinting at an orange sky trying to remember which app you bookmarked last year.
This map is here whenever you need it. Share it with your household. Check it on the days that matter.
Frequently Asked Questions
Is there a wildfire near San Francisco right now?
The live map at the top of this page is the most current answer. It reflects active fire perimeters updated by CAL FIRE and USFS satellite data. Fire conditions change within hours, so use the map rather than information that may already be several hours old. If a fire is affecting Bay Area air quality, it shows on the map as a perimeter boundary, with smoke density visible as an overlay across the affected areas.
How do I check air quality from wildfire smoke in the Bay Area?
PurpleAir shows readings from sensors within a few blocks of your home. AirNow.gov provides regulatory-grade readings by zip code. The two will sometimes show different numbers, which is normal — PurpleAir sensors are more numerous but less precise, while AirNow readings are more accurate but averaged over a wider area. For practical decisions, either source works. When both show AQI above 100, take it seriously.
What does AQI mean for wildfire smoke?
AQI stands for Air Quality Index, which runs from 0 to 500. From 0 to 50 is Good. From 51 to 100 is Moderate. From 101 to 150 is Unhealthy for Sensitive Groups. From 151 to 200 is Unhealthy for Everyone. From 201 to 300 is Very Unhealthy. From 300 up is Hazardous. The dominant pollutant during wildfire events is PM2.5, fine particulate matter smaller than 2.5 microns in diameter that bypasses the body’s normal filtration and reaches deep lung tissue. An AQI of 151 or above means the air is genuinely harmful for all adults.
When is wildfire season in California?
Peak season runs from June through November, with the most destructive fires historically hitting in October and November when Diablo Winds are most active. Fire risk has extended beyond that range in recent years — January and February fires have occurred, and late spring fires are becoming more common as drought conditions persist year-round. Maintain basic smoke preparedness throughout the year, not just during summer and fall.
Do regular HVAC filters help with wildfire smoke?
Only if they are rated MERV 13 or higher. MERV 8, the standard residential filter, lets most PM2.5 pass through. A MERV 8 Dust Defense pleated HVAC filter 6-pack is a practical pre-season stock for your baseline replacement size before you identify a MERV 13 upgrade. MERV 13 is the EPA-recommended minimum for meaningful wildfire PM2.5 capture. Before upgrading, confirm your HVAC system can handle the higher airflow restriction, because some older systems lose efficiency under MERV 13.
Where can I find live evacuation maps for San Francisco?
The SF Department of Emergency Management manages evacuation zones for San Francisco through AlertSF. For orders affecting specific Bay Area counties, Cal OES maintains an address-level evacuation zone lookup at readyforwildfire.org. Check your address there before fire season starts — evacuation zones are categorized by warning level, and knowing yours ahead of time makes a real difference when conditions are moving fast. This map tracks fire and smoke locations but doesn’t issue or manage evacuation orders.
How does wildfire smoke travel to the Bay Area?
Smoke moves at multiple atmospheric levels simultaneously. Near-surface smoke follows local wind patterns. Upper-level smoke can travel hundreds of miles in hours, carried by jetstream-level airflow. The Bay Area receives smoke from fires as far away as Oregon and Idaho during certain atmospheric setups. The Diablo Wind pattern, hot dry air flowing from the northeast, is particularly significant because it both accelerates fire spread and pushes smoke directly toward the coast. NOAA’s smoke dispersion forecasts update daily and show where plumes are expected to move over the next 24 to 48 hours.
Stay Ahead of the Smoke
Wildfire conditions in California shift within hours. The map above gives you live data, but the best preparation happens before smoke arrives.
Three things worth doing now:
• Sign up for AlertSF to receive official emergency alerts for San Francisco.
• Look up your evacuation zone at readyforwildfire.org before you need it.
• Check your HVAC filter and stock a replacement. A MERV 8 Dust Defense pleated HVAC filter 2-pack at Target is a practical baseline, and a pleated MERV 8 AC filter replacement on eBay lets you comparison-shop the size you need before the advisory hits.
Stay informed. Stay safe. Fresh air is worth protecting.