Canadian wildfire smoke turns sky yellow in Boston area, poor air quality around Massachusetts Wednesday

Why has the sky been yellow over Boston? Canadian wildfire smoke will cause poor air quality again on Wednesday in Massachusetts.

A large plume of smoke from the fires unexpectedly poured into the Boston area Tuesday and the skies morphed from a milky white to an ominous brown/yellow.

Boston wildfire smoke

Currently there are more than 800 wildfires across Canada, including a growing cluster just north of the U.S. border near Minnesota.

The winds at upper levels of the atmosphere aligned nearly perfectly to carry the smoke plume more than 1,000 miles, first through southern Canada and then taking a right hand turn directly into New England.  

Why is the sky yellow and orange?

The smoke was thick enough to slow our temperatures from rising into the 90s Tuesday and also to block out the blue light from the sun, much like we see at times during sunset, only the longer wavelength colors were able to pass through the smoke, turning our skies yellow/orange.  

Most models indicate that smoke concentrations will be even higher on Wednesday.

Boston air quality

The thickest smoke will be across northern Wisconsin, northern Michigan, and New York state. This map shows a forecast for near-surface smoke on Wednesday. It's a recipe for very poor air quality in those areas.

In southern New England, you can expect poor air quality for sensitive groups on Wednesday as well as another round of hazy, yellowish skies. You may even be able to smell a bit of the smoke unlike Tuesday

We are lowering our forecast high temperatures on Wednesday by several degrees and lifting the NEXT Weather alert for high heat due to this forecast change.

On Thursday, more wildfire smoke is expected with plumes charging further south and east with devastating effects on air quality for many across the Northeast. As for now, the impacts on visibility will be marginal to moderate.