Why it's smoky, and where the smoke is coming from

Central Oregon · last checked 29 July 2026

The nearest fire is not usually the one you are breathing. Whether smoke ends up in your yard comes down to two numbers that almost nobody publishes in plain English, even though the National Weather Service calculates both of them for this exact patch of ground every hour:

• Transport wind — "the average wind over a specified period of time within a mixed layer near the surface of the earth." Not the wind at your fence line. The wind that actually carries a smoke column.
• Mixing height — "the height to which a parcel of air, or a column of smoke, will rise, mix or disperse." Below it, smoke spreads out. It does not readily get above it.

Put together: the transport wind says which direction the smoke goes, and the mixing height says whether it goes over your head or sits in your living room.

Reading the direction (the part everyone gets backwards)

Wind is always reported as the direction it comes from. A transport wind "from the WSW" is moving air toward the ENE. So if the transport wind is out of the west-southwest, the fires that will smoke you out are the ones west-southwest of you — up the Cascades, or down toward Crescent and La Pine — and the big one east of Mitchell is somebody else's problem that afternoon.

This is why "there's a huge fire twenty miles away and the air is fine" and "the air is unbreathable and there's nothing burning within sixty miles" are both completely normal days here. Direction beats distance almost every time.

Reading the mixing height

A low mixing height is a lid. All the smoke produced under it — from every fire the transport wind is bringing you — gets stirred into a shallow layer of air that includes the air you breathe. A high mixing height is a big room: the same smoke gets diluted through thousands of feet, and a column can punch up and ride over the top of town.

Here is the real forecast for Prineville from the NWS Pendleton grid on 29 July 2026, which is the textbook Central Oregon shape:

At nine in the morning there is a lid at under 2,000 feet and almost no wind to move anything out — that is the hour the smoke is thickest and the sun comes up orange. By two in the afternoon the lid has lifted to over 6,000 feet and the wind has quadrupled, so the same smoke is being diluted and pushed east. By evening it collapses again, cold air slides down the drainages, and whatever is still burning puts smoke back into the valley overnight.

That daily cycle is why:

• The worst air in a smoke event is usually between about 4 a.m. and 10 a.m., not in the afternoon when the fire is most active.
• Smoke settles into the low ground first. The Crooked River valley, the Deschutes canyon and the ranch draws hold it while somebody up on a bench a few hundred feet higher has a clear morning.
• An overnight inversion can make air quality collapse with no new fire growth at all. The fire did not get worse; the room got smaller.

Why a fire 100 miles away can be the one choking you

Big fires generate enough heat to loft smoke thousands of feet up, where it travels in whatever the wind is doing at that level — often for hundreds of miles, over the top of everything in between — and then descends when the airmass subsides or the mixing layer meets it. That is how a fire in southern Oregon or northern California puts Prineville under grey skies while the fire twenty miles up the Ochocos is venting straight up and bothering nobody.

It also means the honest answer to "which fire is this smoke from" is often "several, and one of them is out of state." The agencies that answer that question properly do it with smoke dispersion models, and their products are linked below.

What FireWatcher shows, and what it doesn't

The dashboard shows the two numbers above — transport wind direction and speed, and mixing height — plus surface wind and gusts, humidity, the temperature–dewpoint spread, visibility from the nearest reporting station, and whatever obscuration NWS has in the grid for this point, which during a smoke event says things like "areas of smoke" in the agency's own words. Combined with the fire perimeters and satellite heat detections on the map, you can usually work out for yourself which direction today's smoke is arriving from.

What it does not have is air quality. No AQI, no PM2.5, no sensor readings. That is a deliberate choice: measuring particulates properly is a whole discipline with an existing state-run network behind it, and I would rather point you at people doing it well than put a half-built number on a dashboard next to real ones. For actual air quality, use these:

An example of what a real advisory looks like: on 27 July 2026 Oregon DEQ issued an air quality advisory covering Crook, Jefferson, Wasco and Wheeler counties among others, naming multiple wildfires in southern, central and eastern Oregon as the source, with intermittent smoke expected in Deschutes County. That is the level of specificity to look for — counties, sources, and a time window.

Satellite heat is not the same as smoke

The heat detections on the map come from a satellite instrument that measures thermal energy at 375-metre resolution, a few times a day. It sees fire, through smoke, and it does not measure smoke at all. So a day with few new detections can still be a terrible air day, and a day lit up with detections can be clear at ground level if the mixing height is high and the wind is pushing the plume away from you. Two different questions, two different instruments.

Practical, and then I'll stop

The usual guidance from the state health authority and DEQ, which is worth following because wildfire smoke is genuinely bad for you and not merely unpleasant: keep windows and doors shut during the bad hours, run air conditioning on recirculate, make one room a clean-air room with a filter, skip the run or the yard work, and if you go out in heavy smoke wear a fitted N95 — a bandana or a surgical mask does nothing for particulates this small. If you have asthma, COPD, a heart condition, are pregnant, or are looking after small children or elderly parents, take it more seriously than the rest of us and talk to a clinician about a plan before the smoke arrives. I am not a doctor and this page is not medical advice.

Sources

• NWS glossary definitions of transport wind and mixing height, quoted above.
• NWS Pendleton forecast grid for Prineville — the mixing height and transport wind figures in the table, read 29 July 2026 and converted from metres and km/h.
• Oregon Smoke Information (Oregon DEQ and partners) — the 27 July 2026 advisory and its county list.
• AirNow Fire and Smoke Map; USFS AirFire smoke outlooks; NOAA HRRR-Smoke.
• Oregon Health Authority — prepare for wildfire and smoke.
• NASA FIRMS — the VIIRS thermal detections shown on the map.

Related: Red flag warnings in Central Oregon · What "100% contained" means · Oregon evacuation levels · The aircraft over a Central Oregon fire · All explainers