Bad Air Days in Montrose County, Colorado: under 1 a Year
under 1 bad air days a year
Rare: among the cleanest-air counties EPA monitors. Ranked 859 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (0% particle days).
When the bad days come in Montrose
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June. Averaged over 2016 to 2025.
What actually helps here
- Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
- On the odd bad day, check AirNow and keep windows shut.
Better or worse than it was
The worst recent year was 2018, with 1 bad day on 326 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2018-06-11 | 122 | Ozone |
| 2018-06-19 | 93 | Ozone |
| 2016-06-15 | 84 | Ozone |
| 2018-06-02 | 84 | Ozone |
| 2018-06-24 | 84 | Ozone |
Most days, not the worst ones
Across 922 monitored days from 2016 to 2018, the air in Montrose County rated Good on 87% of them, more often than the 72% typical of monitored counties, and Moderate on 12%. The median day sat at AQI 41; one day in ten went above 55.
The pollutant setting the AQI on an ordinary day here:
- ozone100%922 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2018 | 326 | 257 | 68 | 1 | 0 | 42 | 122 |
| 2017 | 343 | 313 | 30 | 0 | 0 | 41 | 74 |
| 2016 | 253 | 236 | 17 | 0 | 0 | 40 | 84 |
Colorado compared
- Jefferson County28/yr
- Teller Countythin data
- Douglas County20/yr
- Larimer County18/yr
- Boulder County13/yr
- Weld County12/yr
- Arapahoe County12/yr
- Denver County12/yr
How this is counted
A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.