And indeed, that's what it appears to be. This morning's northwesterly winds seem to be carrying a plume of wood smoke across hundreds of miles, from forest fires in the boreal woods of Quebec and eastern Ontario.
Maine's Air Quality Forecast is predicting "Moderate - Limited Health Notice" levels of particulate pollution statewide today, with this explanation:
"Particle pollution values are very high this morning from smoke due to fires in the Province of Quebec. A number of these fires continue to burn out of control. Brisk northwest winds will be directing the smoke and particle pollution toward Maine today. Normally brisk winds cause a lot of mixing and the pollution levels lessen. However, the levels are so high that this turbulence will not be able to completely drop particle pollution levels. In addition, these brisk winds could easily cause these fires to burn more strongly."As of 9 am, though, particulate pollution levels in Portland had exceeded 50 micrograms per cubic meter - a reading that far exceeds "Moderate" levels and approaches the code-red "Unhealthy" status in the federal Air Quality Index.
It's just my luck that I came down with a serious sore throat yesterday - this morning's bad air isn't helping matters.
Elsewhere in the nation, smoke from agricultural burns in the Mississippi River valley and the upper midwest is also blowing into cities across the southeast and midwest. At right is a snapshot of surface smoke in New England at 11 am today, courtesy of the National Weather Service's excellent Air Quality forecasting site.
Visit this link watch the smoke creep towards the ocean over a 12-hour loop of satellite images (choose "1 hour average surface smoke" from the drop-down menu).