As U.S. President Donald Trump formally signed an order doubling tariffs on imported steel and aluminum to 50%, Canada—the largest supplier of these metals to the U.S.—remains significantly impacted.

Prime Minister Mark Carney said Canada won’t respond immediately to the Trump administration’s doubling of steel and aluminum tariffs, and indicated that officials are in “intensive discussions” about the trade relationship between the countries.

Prime Minister Mark Carney says Canada will take "some time" on its response to increased U.S. tariffs on steel and aluminum.

The latest NOAA forecast models foresee smoke persisting in the skies over Philly through the day Wednesday and likely into Thursday. The combination of warmth and the smoke was forecast to drive ground-level ozone to hazardous levels in the afternoon. The region and other parts of the nation are under a “code orange” air-quality alert.

The air quality is reaching dangerous levels in parts of the Upper Midwest and north central U.S., where copious amounts of smoke from wildfires in Canada are wafting south across the international border.