Boston area sky turns yellow as wildfire smoke blocks sun; air quality could be worse on Wednesday

What happened to our sunny, hot and humid Tuesday? And, why is the sky yellow? It's just another case of Mother Nature keeping us New Englanders on our toes, as a large plume of smoke from Canadian wildfires unexpectedly poured into the Boston area on Tuesday.

As morning turned to afternoon, 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 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...this is a recipe for very poor air quality in those areas.

Here in southern New England, we 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, most of the wildfire smoke will have pushed to our south. There may be a small amount of smoke and haze remaining, but we do not expect any major impacts.