Smoke from Canada wildfires may be clearing in US, but watch out for storms, heat

Meteorologists on Saturday alerted millions of residents in Puerto Rico and Texas of potentially dangerous heat conditions, with some ares expecting heat indexes over 110 degrees.

Those warnings, however, are far more localized than the widespread air quality concerns after a smokey haze from Canada's wildfires plagued the eastern United States earlier this week.

On Wednesday, Thursday and Friday, millions of Americans were under Air Quality Alerts along the East Coast in cities like New York, Philadelphia and Washington, D.C. Some schools switched to remote instruction and residents were told to stay indoors or wear protective face masks outdoors.

At the same time, social justice advocates sounded the alarm about the dangers facing cities' most vulnerable residents who live without proper shelter and couldn't easily escape the smoggy air.

Here's what the weeken

• What is the air quality on Saturday? On Saturday, the air had "good" or "moderate" levels of particle pollution along the East Coast's I-95 corridor, meteorologists said. There may still be some hazy smoke visible in the skies Saturday in major cities like New York and Philadelphia, but it will be in higher levels of the atmosphere, said NWS meteorologist Zack Taylor from the Weather Prediction Center. It should not affect people's breathing.

• Why did the air quality improve? Shifting winds have allowed the smoke to be more dispersed, according to meteorologists at the National Weather Service's Weather Prediction Center.

d weather forecast in the US:

• Parts of the Midwest will still have poor air quality: There will still be "pockets" of poor air quality in places like Detroit, Indianapolis and parts of Ohio, he said, which are "unhealthy for sensitive groups or just generally unhealthy for most people," he said.

• NWS explains: "The smoke is not nearly as dense or as widespread this morning and this weekend and that's why the air quality levels are much improved, particularly across the Mid-Atlantic and the northeast," Taylor told USA TODAY.

US air quality map

Extreme heat in Puerto Rico, South Texas

Virtually all of the island of Puerto Rico is under some form of heat alert Saturday, as the heat index temperatures could reach over 110 degrees Fahrenheit, according to the weather service.

"The combination of hot temperatures and high humidity will create dangerous situations in which heat related illnesses are possible," the weather service says on its website.

Experts warned residents Saturday to reschedule strenuous outdoor activities to the morning or evening, and to watch for signs of heat exhaustion.

Similarly, cities in South Texas like Corpus Christi, Victoria and Laredo are under a heat advisory from noon until 7 p.m. Saturday, with the heat index temperature expected to reach 110 degrees or higher, according to the NWS.

"Please take frequent breaks and drink plenty of water if you must be outside today," experts at the weather service warned online Saturday.

Thunderstorms in the South

Parts of East Texas, Louisiana and Arkansas are expecting severe thunderstorms Saturday that could unleash damaging winds and hail, the weather service said on Twitter.

US weather watches and warnings map

Air quality much improved in eastern US

Air quality along huge stretches of the East Coast has improved since Wednesday and Thursday, when residents faced dangerous levels of pollution from smoke that drifted into the U.S. from hundreds of wildfires in Canada. The concerns were worsened by fires in the U.S. as well.