Smoke from hundreds of wildfires burning across Canada blanketed large portions of the United States on Thursday, triggering widespread air quality alerts from the Upper Midwest to the Northeast.

Over 830 wildfires continued to burn across Canada, along with over a dozen active fires in northern Minnesota. The blazes have forced mandatory evacuations and sent thick smoke drifting south, affecting millions of people across the Lower 48 states.

In New York City, a hazy orange sky shrouded the city's iconic skyline as air quality deteriorated throughout Wednesday. Officials warned that unhealthy conditions were expected to persist into Thursday.

New York authorities issued an Air Quality Health Advisory covering the entire state, urging residents to limit outdoor activities.

"Air quality has reached unhealthy levels in parts of NYC due to smoke from Canadian wildfires," New York City Mayor Zohran Mamdani said in a statement.

He warned that poor air quality poses heightened health risks for people with heart or lung conditions, older adults, pregnant women, infants, and children, encouraging residents to remain indoors in air-conditioned environments whenever possible.

City officials also distributed free protective masks to help residents cope with the smoky conditions.

Air monitoring data showed unhealthy air quality levels across New York City, the Eastern Lake Ontario region, Central New York, and parts of western New York.

The largest wildfires are burning in west-central Ontario, where dense forests continue to fuel massive fires and generate enormous amounts of smoke.

Prevailing winds have carried the smoke deep into the United States, with heavy concentrations reported across Minnesota, Wisconsin, Michigan, New York, and New England.

Very heavy smoke covered Duluth, Minnesota, and Marquette, Michigan, while northern Wisconsin experienced some of the worst conditions. Hazy skies extended eastward toward Boston by Wednesday evening.

Although officials noted that current conditions are not expected to reach the severity of the June 2023 wildfire smoke event that turned New York City's skies a vivid orange, air quality remains hazardous for millions.

Rain forecast for the Upper Midwest on Friday and the Northeast on Saturday is expected to help disperse some of the smoke.

The wildfire smoke has coincided with an intense heat wave affecting much of the United States.

Temperatures across the Northeast and Upper Midwest climbed into the upper 90s and exceeded 100 degrees Fahrenheit in some locations.

Heat index values—the "feels like" temperature—were forecast to reach 104 degrees in New York City, 105 degrees in Washington, D.C., and as high as 107 degrees in Philadelphia.

Minneapolis remained under an Extreme Heat Warning through Thursday, with heat index values approaching 100 degrees.

Southern California also faced dangerous temperatures, prompting an Extreme Heat Warning for parts of the Los Angeles area through Thursday night.

Los Angeles and Orange counties were expected to reach around 96 degrees, while California's San Joaquin Valley saw temperatures climb above 100 degrees, including forecasts of 104 degrees in Fresno and 105 degrees in Bakersfield.

Meanwhile, severe weather continued in Texas, where heavy rainfall raised the risk of dangerous flash flooding across the Hill Country.

Between 6 and 16 inches of rain had already fallen in parts of the region this week, leading to numerous water rescues.

Forecasters warned that an additional 6 to 12 inches of rainfall could fall across parts of south-central Texas, including Loma Alta, Uvalde, and San Antonio, with isolated areas potentially receiving up to 20 inches.

Authorities also reported that multiple witnesses observed a tornado touching down near San Antonio on Wednesday morning. No immediate reports of injuries or significant damage were available.

Meteorologists warned that the combination of hazardous air quality, record-breaking heat, and severe flooding poses multiple risks to public health and safety, urging residents in affected regions to closely monitor weather advisories and follow guidance from local officials. (ILKHA)