There was no wood smoke all morning and no wood smoke all day until evening. The morning temperature was 12 degrees. As cold as it was, nobody seemed to be burning wood for home heating during the daylight hours.
4:30 PM: No smoke. 25 degrees.
5:45 PM: A very faint trace of wood smoke is in the air. It is barely noticeable.
7:25 PM: No smoke. The air is not fresh at this time. Something is in the air at a level insufficient to determine what it is.
9:15 PM: Moderate wood smoke. The air is very smoky at this time.
10:00 PM: Moderate wood smoke continues.
11:00 PM: No real smoke. The air is mostly clear at this time.
When I woke after 1 AM the air was fresh and clear.