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Canadian Wildfire Smoke Chokes Montreal and New England, Prompting Health Advisories

By trapping fine particles over southern Quebec and the U.S. Northeast, a sinking mid-level air mass drove Montreal to the top of global pollution rankings.

The skies weren't exactly clear in New York City over the weekend.
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Stock photograph showing smoke from the Dragon Bravo fire filling the Grand Canyon along the South Rim near the Yavapai Geology Museum on July 17, 2025 in Grand Canyon, Arizona.
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Overview

  • Record-scale wildfires in Canada’s Prairies have sent dense smoke plumes across the border, degrading air quality from southern Quebec to New England and Colorado’s Mesa County.
  • Environment Canada alongside Vermont, Maine and New York agencies issued air quality alerts urging sensitive groups to limit outdoor exertion and watch for respiratory symptoms.
  • Montreal briefly logged the world’s worst air quality on Saturday according to IQAir as PM2.5 levels spiked under stagnant atmospheric conditions.
  • New York State’s DEC and DOH health advisory covered Long Island, New York City, Hudson Valley and the Adirondacks from 10 a.m. to 11:59 p.m. Saturday amid AQI readings above 100.
  • Forecasters expect some clearing late Sunday evening but caution that shifting winds could bring another wave of wildfire smoke back over the region.