Biden orders more firefighters, aid to Canada as smoke engulfs Washington

President Joe Biden on Thursday announced he is sending additional firefighters and aid to Canada as the nation battles ongoing wildfires that's left the northeastern U.S. engulfed in heavy smoke.

Biden called the fires "another stark reminder of the impacts of climate change" and said he's directed the National Interagency Fire Center to respond to Canada's needs for more manpower and equipment after speaking with Canada's Prime Minister Justin Trudeau.

"We already have 600 American firefighters on the ground, and have been there for a while in Canada, including hotshots and the smokejumper crews," Biden said as he addressed the issue at a press conference alongside United Kingdom Prime Minister Rishi Sunak.

Biden urged Americans to follow guidance from local and state officials and to use airnow.gov to check on air quality in real time, even holding up a photo of what the app looks like.

Air quality alerts have been issued in at least 20 states and Washington, D.C., with wildfire smoke expected to impact the East Coast and mid-Atlantic through Friday. Winds are expected to shift and blow smoke away from the U.S. by the weekend.

The White House postponed its Pride celebration set for Thursday evening due to hazardous air conditions from wildfire smoke.

Biden was set to host hundreds of LGBTQI+ families and kids from across America at 7 p.m., with a performance from singer Betty Who, in what administration officials said would be the White House's largest-ever Pride event.

But the Washington region early Thursday was put under a Code Purple alert as smoke continues to choke major U.S. cities, including Philadelphia and New York.

As of Thursday afternoon, Washington had a worse air quality index than New York City.

The Metropolitan Washington Council of Governments recommended sensitive groups, including children and older people, to avoid all physical activity outdoors and everyone else to consider rescheduling or moving activities indoors.

The poor air quality prompted Major League Baseball to postpone the Washington Nationals game and the National Zoo in Washington to close its doors "for the safety of our animals, our staff and our guests."

Senate Majority Leader Chuck Schumer, D-N.Y., addressed the wildfire smoke on Thursday. Like Biden, he said "we cannot ignore that climate change continues to make these disasters worse."

"None of this is coincidence. This smoke and fog over New York and the rest of the northeast is a warning from nature that we have a lot of work to do to reverse the destruction of climate change," he said, urging his colleagues to do more to address the issue.

"Both parties have an obligation to do more. The work to protect our climate is far from over and we are dangerously behind," Schumer said. "I implore my colleagues on both sides of the aisle to look up at the smog today and recognize that we must do more."

-ABC News' Allison Pecorin contributed to this report.