As best we can tell, on June 1st, Lightning struck in Quebec Province, Canada, kindling

large fires, the smoke from which drifted down to the eastern seaboard and the Midwest,

leaving it in a haze.

Today in Canada, 497 wildfires are burning, according to the Canadian Interagency Forest

Fire Center, and 229 of them are out of control.

Canada's smoke has reached Portugal and France, and forecasters say, it might be with us

in the US on and off until October.

100 million Americans are living with what we're told is bad air.

So we're going to explain your air quality indices, your code reds versus code purples,

the weather patterns that got us here, the experts' top predictions for the summer.

It's going to be really hot.

And the best advice we've heard on how we can survive and thrive, or at the very least

cope with extreme heat that's coming up on today's Blaine.

It's today explained, I'm Noel King.

Rebecca Lieber is a climate change reporter at Vox.

She recently wrote a very good piece about how, once upon a time, the air quality in the

United States was very bad, and then it improved, and then it got bad again.

I asked Rebecca to take us back to the beginning.

Our pollution in the US was famously bad before we had environmental regulation.

Industry and cars all were producing this haze and smog that you could visibly see in

the air.

Here we are.

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