These two images show the distribution of smoke from wildfires. Most of what residents in the United States will see and smell today is coming from fires in Canada, but wildfires in Washington and Oregon are also contributing to the haze, but in comparatively small amounts.
The image above is a forecast for smoke at 4 p.m. MT, July 2, 2015. Below is a “smoke analysis” for July 2, 2015, produced by NOAA. The red dots represent the location of wildfires.
It has been overcast here in central PA most of the day, I thought it was likely smoke since the weather forecast called for sunny skies!