Seasonal · 7 min read
Salt Lake City inversion season 2026–27: when it starts, Utah's burn rules, and how clean the air is now
Salt Lake City inversion guide for winter 2026–27: Utah's wood-burning rules from 1 November, how often PM2.5 spikes, and how the air looks before it starts.
By the Good Air team
In this article · 9 sections
Salt Lake City's inversion season, when cold air traps smog in the Salt Lake Valley, usually starts around Thanksgiving, and Utah's seasonal wood-burning restrictions begin on Sunday 1 November 2026 and run to 1 March 2027. In a typical winter, the valley sees about six multi-day inversion episodes and 18 days when fine-particle pollution (PM2.5) breaks the federal standard (University of Utah, last edited 26 September 2016).
Before the season starts, Salt Lake City's air is already a little worse than most of the country. From 15 September to 20 October 2026, Salt Lake City's average daily US AQI was 49, 29th highest among the 266 US cities we track, against a median of 37. Its air was Moderate on 17 of 35 days, when the median city had 4. But PM2.5 at northern Utah's monitors stayed far below inversion levels, and the highest day at any of them was 19.9 µg/m³.
Key facts for winter 2026–27
- Season: wood-burning restrictions run from 1 November to 1 March, though no-burn days can be called at other times (Salt Lake City Green Blog, 10 December 2025).
- Burn levels: Utah's Division of Air Quality (DAQ) calls Unrestricted, Voluntary Action or Mandatory Action days. There are no official "red" or "yellow" burn days.
- Salt Lake County is stricter: it bans burning on Voluntary Action days too.
- How to check: air.utah.gov, the UtahAir app, or 1-800-228-5434. Our Salt Lake City page shows Utah DEQ's daily forecast for today and tomorrow, via AirNow.
What is an inversion, and why does the Salt Lake Valley trap pollution?
Normally, air cools with height. In an inversion, cold air sits on the valley floor under a layer of warmer air that acts as a lid, trapping pollution from cars, homes and industry as haze (KUER, 6 January 2025).
The Salt Lake Valley floor lies at about 1,300 metres (4,300 feet), with the basin rim averaging about 2,200 metres (7,200 feet). When a winter high-pressure ridge crosses Utah, the air in that bowl stops mixing (University of Utah). A 40-year study by University of Utah meteorologists found that most winter exceedances come from a few such multi-day spells, when valley air is cold, humid and calm, and that snow cover makes high readings much more likely (Whiteman and others, Atmospheric Environment, September 2014).
On 12 January 2026, during an inversion, Salt Lake City reached 40°F while a National Weather Service (NWS) site at Alta, a few thousand feet higher, reached 48°F (KSL, 13 January 2026).
When is inversion season in Salt Lake City?
KSL meteorologist Grant Weyman has said Utah's smog season typically starts around Thanksgiving (26 November in 2026), with hazy skies sometimes earlier (KSL, 11 November 2019).
As of 22 October, nothing points to an early start. The NWS in Salt Lake City expected a storm on 22 and 23 October, with snow above 9,000 feet in the northern mountains, then drier, seasonal weather, with low confidence in the pattern (NWS Salt Lake City forecast discussion, 21 October 2026).
How bad does the air get?
The federal 24-hour standard for PM2.5 is 35 µg/m³ (EPA, updated 21 October 2026). A typical Salt Lake Valley winter breaks it on about 18 days, spread over about six episodes. Long episodes can run for over a week: one in February 2016 exceeded the standard on 8 consecutive days (University of Utah).
In January 2026, several Salt Lake Valley cities had the worst air in the country on 12 January on IQAir's monitor network, at levels Unhealthy for Sensitive Groups, and DAQ ordered mandatory action, banning solid-fuel burning (KSL, 13 January 2026).
The American Lung Association's State of the Air 2026 report ranked the Salt Lake City–Provo–Orem metro area 22nd worst in the US for short-term particle pollution, with Salt Lake County averaging 7 unhealthy days a year from 2022 to 2024. The Logan metro area ranked 24th, with 5.8 days a year in Cache County (American Lung Association, 21 April 2026).
Utah's burn rules: unrestricted, voluntary and mandatory action days
DAQ announces one of three action levels each day (Utah Department of Environmental Quality news release via Utah Policy, 28 October 2022):
| Action level | Symbol | What it means |
|---|---|---|
| Unrestricted | Black circle | Stoves and fireplaces may be used; burn cleanly |
| Voluntary Action | ▼ | Please don't burn wood or coal, and drive less. Banned in Salt Lake County |
| Mandatory Action | X | Burning wood or coal is prohibited. Fines up to $299 per day |
Under Utah's rule, a mandatory no-burn period is triggered when PM2.5 is forecast to reach or exceed 25 µg/m³, or 15 µg/m³ where a pollution contingency plan is in force. It covers parts of Box Elder, Cache, Davis, Salt Lake, Tooele, Utah and Weber counties. For homes, the main exemption is a stove registered with DAQ as the only source of heat (Utah Administrative Code R307-302-3, via Cornell LII, viewed 22 October 2026); Tooele County says only stoves registered by 1 June 2013 qualify (Tooele County Health Department, viewed 22 October 2026).
"Solid fuel" includes pellet stoves, fire pits, charcoal grills and smokers, but not gas or propane, and burn indicators use symbols, not colours (Davis County Health Department, viewed 22 October 2026). The green, yellow, orange and red ratings behind the phrase "red air day" are DAQ's separate daily health guidance, based on PM2.5 (Utah DEQ, 28 October 2022). Our most recent DAQ source on fines is from 2022, so check air.utah.gov before you light a fire.
The air before the season: our autumn baseline
Readings from EPA AirNow monitors, 15 September to 20 October 2026:
| City | Average daily US AQI | Rank of 266 | Days above 50 (of 35) |
|---|---|---|---|
| Salt Lake City | 49 | 29 | 17 |
| Provo | 39 | 107 | 1 |
| Median US city | 37 | 4 |
Salt Lake City's daily average was above the US median on 32 of 35 days, and its worst day was 7 October, at 64. In the hourly data we hold for 13 to 21 October, PM2.5 set Salt Lake City's AQI in 161 of 209 hours and ozone in 44. Pleasant Grove had too few complete days to rank.
The individual monitors tell a calmer story. The median US PM2.5 monitor averaged 5.2 µg/m³ over the period, among 1,256 that measure it. Northern Utah's monitors were close to it:
| Monitor (AirNow name) | Area | Average PM2.5 (µg/m³) |
|---|---|---|
| NR | Salt Lake County | 7.2 |
| Smithfield | Cache County, near Logan | 6.3 |
| Hawthorne | Salt Lake City | 5.6 |
| BV | Davis County | 5.6 |
| Lindon | Utah County | 5.1 |
| Harrisville | Weber County, near Ogden | 4.5 |
The highest day at any of the 20 northern Utah monitors in our archive was 19.9 µg/m³, at BV on 7 October, when Salt Lake City's AQI also peaked. Smithfield reached 18.2 on 2 October. No monitor came near the 25 µg/m³ no-burn trigger.
So Salt Lake City's higher AQI this autumn comes from frequent Moderate hours, not heavy pollution. The most polluted cities in our autumn ranking of US cities were in California's San Joaquin Valley. For today's numbers, see the live US air quality ranking.
How to tell an inversion is setting in
- A storm has just passed and high pressure is building, with calm winds and cold, clear nights. Inversions typically form in a lull between storms (KSL, 13 January 2026).
- Snow covers the valley floor (Whiteman and others, 2014).
- The haze thickens each day while the mountains above stay sunny.
- The forecast turns yellow, then orange. Our Salt Lake City and Provo pages show Utah DEQ's AQI forecast for tomorrow, via AirNow. Our Utah weather alerts page lists active NWS alerts.
Protecting yourself: exercise and indoor air
At Unhealthy for Sensitive Groups (US AQI 101 to 150), members of sensitive groups may feel effects; at Unhealthy (151 to 200), some of the general public may too (AirNow, viewed 22 October 2026). During the January 2026 episode, the NWS advised people to stay indoors as much as possible, telework or take transit, and wear a mask that filters PM2.5 outdoors (KSL, 13 January 2026).
- Move exercise indoors or shorten it once the AQI passes 100, sooner if you have asthma. See what AQI is safe for running and cycling.
- Keep windows shut until a storm clears the inversion, and run a HEPA air purifier in the bedroom.
- Don't add smoke indoors: seal draughts to keep warm instead of lighting a fire (Salt Lake City Green Blog, 10 December 2025).
How we measured
- Data. EPA AirNow's hourly US AQI for each city and PM2.5 at each monitor, collected by Good Air. Government monitors only.
- City values. The mean of each day's hourly AQI (days with 12+ hours), then the mean of those days. Cities needed 31 of the 36 days from 15 September to 20 October 2026 (UTC): 266 qualified. AirNow's city value follows the highest-reading nearby monitor and pollutant each hour, so it runs higher than any one monitor's average.
- Monitors. Means of daily PM2.5 averages, monitors with 31+ valid days: 1,256 in the US, 20 in northern Utah.
- Limits. An autumn baseline says nothing about how bad this winter will be.
Frequently asked questions
When does inversion season start in Salt Lake City?
Salt Lake City's inversion season usually starts around Thanksgiving, which falls on 26 November in 2026, though haze can appear earlier. Utah's seasonal wood-burning restrictions begin on 1 November 2026 and run to 1 March 2027. The worst episodes come in calm, cold spells under winter high pressure, often after snow.
How many inversion days does Salt Lake City get?
University of Utah research based on 40 years of data found that a typical Salt Lake Valley winter has about six multi-day inversion episodes and 18 days when PM2.5 exceeds the federal 24-hour standard of 35 µg/m³. Some winters are much worse than others, and one February 2016 episode broke the standard on 8 days in a row.
Can I use my fireplace today in Salt Lake County?
Check air.utah.gov, the UtahAir app or 1-800-228-5434. Salt Lake County bans burning wood and other solid fuels on both Voluntary Action and Mandatory Action days. Elsewhere on the Wasatch Front, burning is banned only on Mandatory Action days, when fines can reach $299 per day.
What is a red air day in Utah?
"Red air day" refers to the colour scale of Utah's daily health guidance, which rates PM2.5 green, yellow, orange or red. Burn restrictions are separate: the Utah Division of Air Quality labels them Unrestricted, Voluntary Action or Mandatory Action, using symbols rather than colours. A mandatory day is called when PM2.5 is forecast to reach 25 µg/m³.
Is Salt Lake City air quality bad right now?
From 15 September to 20 October 2026, Salt Lake City averaged a US AQI of 49, higher than the US median of 37 but still in the Good range, with PM2.5 far below winter inversion levels. For the current reading and Utah DEQ's forecast for tomorrow, see the live Salt Lake City air quality page.
