When will Philadelphia’s air quality get better? Here’s the latest forecast.
The latest forecast did not call for any rain overnight or even much of Saturday. Rain would help clear any lingering smoke.
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Philadelphia’s air quality continued to be poor Friday, as smoke from wildfires in Canada lingered across the region.
Philadelphia, Pennsylvania, and Delaware issued “code orange” alerts for Friday, meaning the air quality was slightly better than Thursday but remained poor.
A “code orange” means smoke concentrations are unhealthy for sensitive groups, which includes children, the elderly, and people suffering from heart disease, asthma, or other lung diseases.
The air quality index in Philadelphia as of 5 p.m. was 165, according to government data, enough to place the city in the category of “unhealthy” for all. City officials said they expected the air quality to improve throughout the afternoon — though evening readings seemed to worsen slightly — and city pools and outdoor summer camps were operating normally Friday.
Despite the improving air quality, smoke lingered across the region.
The National Weather Service in Mount Holly issued a forecast Friday evening that said winds will continue to clear out the haze over the region, though some of it will remain until rain or stronger winds sweep it away.
The latest forecast, however, did not call for any rain overnight or even much of Saturday.
Apart from the hazy skies, the weather was seasonal on Friday, with temperatures in Philadelphia recorded in the mid-80s, with less humidity than previous days.
The city encouraged those in sensitive groups to:
Choose less strenuous activities (like walking instead of running) so you don’t breathe as hard.
Shorten the amount of time you are active outdoors.
Be active outdoors when air quality is better.
Consider wearing a high-quality mask to limit your exposure to pollutants.
What is the air quality index?
The U.S. Environmental Protection Agency pulls data from gauges that measure various pollutants in real time. In this case, the EPA uses data collected by Philadelphia’s Air Quality Management Services.
The EPA sets limits for each pollutant for its air quality index (AQI). The level of each pollutant is color-coded based on the highest daily AQI value at selected monitors. The Philadelphia Health Department lists six levels, from lowest to highest: green, yellow, orange, red, purple, and maroon — a level considered “hazardous.”
Earlier this month, Philadelphia reached the maroon level, the worst air quality since at least 2008 if not before, according to historical EPA data. The poor air quality forced people across the city indoors and led to several events, including a Phillies game, to be canceled or postponed.
What is PM2.5?
PM2.5 is fine particulate matter defined as concentrations of 2.5 microns or smaller. It’s of special concern because the particles are so small — far smaller than the width of a human hair — and are easily inhaled. The World Health Organization says PM2.5 is responsible for the biggest proportion of health effects from air pollution.
Locally, the biggest typical sources of PM2.5 are emissions from gas and diesel-powered vehicles. Power plants are also a source. The particles form when emissions react in the air.
But wildfires burning in multiple Canadian provinces and territories contain a mixture of gaseous pollutants and PM2.5 is a chief component.
Particle pollution refers to a mix of solid and liquid droplets in the air. Some particles are so small that they are visible using only an electron microscope. Those particles can penetrate both indoors and outdoors because of their small size. During wildfires, concentrations can rise so high that particles are visible to the naked eye as part of the mix of gases in a haze.
Staff writer Frank Kummer contributed to this article.