While I was a kid growing up in the 60’s and 70’s on the edge of Los Angeles, there were several fires that came within threatening distance.
In LA in those years thick air was not so uncommon (air quality in LA is noticeably improved now, even with millions more people and cars) but when a wildfire was approaching it would start to get a woody, campfire quality. There is a lot of wild sage and manzanita and other pungent plants on California mountains and that stuff can hit your in the eyes and throat.
Then the sky turns a weird color, the air gets funkier and has noticeable particulate, eyes and throat sting more. Pets are upset; they disappear or stick really close to you, agitated.
When you see the fire climb over the ridge line to your side of the hill, it becomes very real and you start to wonder if you might have to leave your home. And wonder about what you might come back to…
Fortunately we never did have to evacuate. But after a few hours or days of acrid smoke you might wish you had gone somewhere else for a while anyway.