Why is it so smoky?
Because the wind is carrying smoke from a fire, sometimes hundreds or thousands of miles away, and a lid of warm air is holding it close to the ground.
Smoke can sting your eyes and dim the sun.
Fine particles reach deep into your lungs.
Show me why1 min
Smoke travels with the air
A big wildfire can loft smoke thousands of feet up, where stronger winds carry it across states and even oceans. Smoke from Canadian fires has turned skies hazy and orange over US cities far to the south. Whether it reaches you depends on where your air came from, which is exactly what Air Story's three-day trail shows.
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The lid that traps it
Normally air gets cooler with height, so warm air near the ground rises and carries smoke up and away. Sometimes a layer of warmer air sits on top instead. This temperature inversion acts like a lid: smoke and pollution under it can't escape, so they build up near the ground, especially overnight and in valleys.
Thick smoke can even strengthen its own lid. It shades the ground, the ground stays cooler, and the inversion holds. University of Utah researchers measured exactly this in smoky valleys.
What smoke does inside you
The harmful part is fine particles called PM2.5, about 30 times thinner than a human hair and small enough to reach deep into the lungs. The US Air Quality Index turns them into one number. Above 100, people with asthma or heart or lung disease, children and older adults should cut back on hard outdoor activity; above 150, everyone should. Closed windows and a good air filter help indoors.
Questions people ask
- How far can wildfire smoke travel?
- Hundreds to thousands of miles. Smoke lofted high can cross a continent, while smoke near the ground stays more local.
- Why is smoke worse in the morning?
- Overnight the ground cools and an inversion often forms, trapping smoke near the surface. Afternoon sun usually mixes the air and can thin it out.
- Why does the sun look orange in smoke?
- Smoke particles scatter blue light away and let red and orange through: the same effect as a sunset, only stronger.