Wildfire smoke pushed air-quality advisories across western Colorado this weekend, from Grand Junction to Telluride to Steamboat. Hiking in wildfire smoke is not just a hazy inconvenience. Here is how to read the air-quality index and decide when it is too smoky to hike.
If the mountains looked wrong this weekend, you were not imagining it. Smoke from the Snyder Fire and the other fires burning across the Western Slope turned the sky a flat tan from the Grand Valley to the San Juans, and Colorado public-health officials issued air-quality advisories for much of western Colorado. A smoky sky is easy to shrug off. For anyone planning to hike, it is worth taking seriously, because the same effort that makes a summit feel good is the thing that pulls smoke deep into your lungs.
What is happening
As of Sunday, June 28, the Colorado Department of Public Health and Environment had air-quality advisories up for much of the Western Slope, including Mesa, Garfield, Routt, Eagle, Montrose, Delta, Gunnison, and Pitkin counties. CBS Colorado reported that Telluride, Montrose, Grand Junction, Gunnison, Aspen, Glenwood Springs, Steamboat Springs and other mountain towns could see periods of heavy smoke and reduced visibility, with moderate to heavy smoke expected to linger at least through Sunday morning. Forecasters expected the smoke to drift east later in the day, hazing the Front Range and the Denver metro by evening.
The source is the cluster of fires we covered separately: the Snyder Fire near the Utah line, which has burned more than 28,000 acres with no containment, plus the Gold Mountain Fire near Ouray and several fires in the San Juan National Forest.
Why smoke hits hikers harder
The thing that makes wildfire smoke dangerous is not the smell. It is the fine particles, called PM2.5, that are small enough to slip past your body’s defenses and lodge deep in your lungs and bloodstream. The Environmental Protection Agency points to those particles as the main health threat in smoke.
Hiking makes it worse in two ways. You breathe harder and deeper when you climb, so you pull more of those particles in. And you are usually doing it at altitude, where your lungs are already working overtime. So the exact moment you feel proud of the effort is the moment you are taking in the most smoke. People with asthma, COPD, or heart conditions, older adults, kids and teenagers, and pregnant women are the most vulnerable, but on a bad-air day, smoke is hard on everyone.
How to read the air-quality index
You do not have to guess. The air-quality index, or AQI, is a 0-to-500 scale the EPA uses to turn pollution into one number and one color. Here is what the bands mean for a hiker, per AirNow:
- 0 to 50 (green): good. Hike normally.
- 51 to 100 (yellow): moderate. Fine for most people, though the unusually sensitive may feel it.
- 101 to 150 (orange): unhealthy for sensitive groups. If you have a heart or lung condition, this is your line.
- 151 to 200 (red): unhealthy. Everyone can feel it, and a hard effort is a bad idea.
- 201 to 300 (purple): very unhealthy. Stay off the trail.
- 301 and up (maroon): hazardous. Stay inside.
One habit matters more than any single reading: check the AQI the morning you go, not the night before. Smoke drifts and settles overnight, and a valley that was clear at dinner can be socked in by sunrise. The free AirNow app and its companion smoke map show both the current reading and the plume forecast. Our guide to the best free hiking apps every Colorado hiker should have walks through setting them up.
When it is too smoky to hike
None of this has to be complicated. Treat these as rules of thumb rather than medical advice, and lean conservative when you are unsure:
- Above an AQI of 100, scale it back, especially anything above treeline where you cannot bail out quickly.
- Above 150, most people should skip a hard effort. Trade the 14er for a short, low walk, or take the rest day.
- Above 300, stay home. No view is worth it.
- Pick lower, shorter, and earlier. Smoke often pools in the valleys overnight and lifts a little by midmorning, and lower elevation means easier breathing.
- Do not count on a mask. Cloth and surgical masks do little against fine smoke, and while a well-fitted N95 helps at rest, you cannot hike hard in one for long.
- Listen to your body. A cough, a headache, a scratchy throat, or tightness in your chest is your cue to turn around, not to push through.
- If you are in a sensitive group, sit the worst days out. The trail will still be there when the air clears.
We say it a lot around here: risk management is not fear, it is smart. Smoke is one of the easiest risks to manage, because the information is free and the fix is patience. The summit keeps. Your lungs are the one piece of gear you cannot replace.
Reporting from CBS Colorado and the Colorado Department of Public Health and Environment, with health guidance from the EPA’s AirNow program. Smoke and air quality change fast, so check AirNow and the Colorado smoke advisory the morning of your hike.
