Washington Dept of Ecology 5-day smoke forecast
CalTopo -- in the Map Layers side panel on the right, click Fire Activity checkbox. There's a small key you can bring up from the tiny button that says "Fire Info" in the bottom center of the map.
Air Purifying
Wirecutter air purifier recommendations -- we have the Coway Mighty (AP-1512HH) and another from Honeywell that's no longer on sale.
Last year when we had smoke for almost three weeks we felt sick partly because we could never get clean air into the house. This year we bought two box fans (~$20 each new, like this) and a box of furnace filters (~$40 for six). Our plan is to tape the filters on the fans, to be able to open the windows and "wind tunnel" the house once a day or so. Then we'll shut the windows again and turn the air filters on high. These two articles describe the DIY-ish type solution we're trying.
People also build a bigger DIY filter out of a box fan and two to five filters, called a "Corsi-Rosenthal cube". Construction described here.
Other things to do
If you're in Seattle, you can email your councilmember to ask that they start to prepare smoke shelters for people living unsheltered. I did.