“The sky is hazy due to wildfire smoke from Canada,” tweeted the National Weather Service Pittsburgh account on July 19.
Fires in Canada aren’t the only reason for the smoke spreading thousands of miles over North America. According to a press release from weather media company AccuWeather, there were nearly 120 wildfires burning across the western U.S. as of July 19. At least 60 of those were considered to be large and uncontained, according to the U.S. Forest Service.
The sky is hazy due to wildfire smoke from Canada. ☁️ Below is a link to the high resolution model (HRRR) that helps forecast vertically integrated and near-surface smoke potential in the near term...https://t.co/OF9Gl7yLsi— NWS Pittsburgh (@NWSPittsburgh) July 19, 2021
"Due to the fact that smoke particles are small and light, they can be transported hundreds if not a few thousand miles away from their source," says AccuWeather Meteorologist Alex DaSilva in a press release.
Correspondingly, the Pittsburgh area has been issued a Code Orange air quality alert for July 20. This means that the air quality is unhealthy for sensitive groups of people, including those with respiratory problems like asthma or emphysema, or the elderly. Usually, poor air quality in Pittsburgh is caused by temperature inversions that trap industrial pollutants near the surface. But the wildfires from far-flung areas are the main culprit this time around.
The Pennsylvania Department of Environmental Protection encourages people to avoid using fireplaces for wood stoves, or gas-powered lawn and garden equipment during air quality action days.