Wildfire smoke is driving terrible air quality in major cities, but relief is coming

By Meteorologists Dakota Smith, Brandon Miller, CNN

(CNN) — Thick, choking plumes of smoke from wildfires in Canada are pouring into major cities across the Midwest, Northeast and mid-Atlantic, bringing dangerous air quality to more than 100 million people. The polluted air will last through at least Saturday in some areas as new waves of smoke waft south.

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Here’s the latest:

• Millions affected: More than 100 million people in 18 states and the District of Columbia are under air quality alerts. “Very unhealthy” and “hazardous” air quality stretches from northeast Minnesota to southeast Virginia.

• Widening reach: Smoke is being carried south Friday, and Washington, DC, is now experiencing dangerous air quality. But the smoke is still on the move: weather patterns will determine which cities have the worst air quality each day.

• Relief is coming: Multiple rounds of thunderstorms are possible from the lower Great Lakes into the Northeast on Saturday. Wildfire smoke may still cause hazy skies and unhealthy air, especially early Saturday, but we expect it to thin from west to east. Rain, shifting winds and a cold front should eventually help clear the smoke, though air quality may not improve everywhere immediately.

• Where it’s worst: Milwaukee, Chicago, and Detroit had some of the worst air quality in the country Friday morning, but dangerous levels of pollution stretched into southern Ohio and West Virginia.

“Chicago is currently experiencing its worst air quality in recorded history,” the mayor’s office said in a social media post Thursday evening. “Please stay indoors, and if you must go outdoors, use a well-fitted N95 or KN95 mask for your safety.”

The Detroit Health Department is offering free masks to residents on Friday and encouraging everyone to stay inside. In Philadelphia, “everyone is likely to experience health effects from being exposed” to smoke in the air Friday, officials warned in a media release.

Track the smoke

Smoke has already been an issue this summer in parts of the West, Plains and Midwest as stateside fires have burned more than 3.6 million acres, mostly in the western half of the country. But the thicker smoke that has moved in this week is from wildfires to the north.

In Canada, 3,500 fires have burned more than 6 million acres this summer, with a dozen blazes flaring up in Ontario in recent weeks, filling the skies with smoke drifting south, like it did in an extreme way in 2023.

Canadian wildfire activity this year is nowhere near the hyperactivity of 2023 but the combination of wildfires in Ontario and a heat dome in the central US spells smoky trouble for millions.

Planet-heating fossil fuel pollution is increasing the chance of prolonged smoke seasons as it tips the odds that extreme wildfire seasons like 2023’s — Canada’s worst season on record — won’t remain an outlier for long.

Wildfire smoke contains dangerous, tiny pollutants called PM2.5 that can travel deep into the lungs or enter the bloodstream when inhaled. The minuscule particles can lead to breathing problems like bronchitis and cause inflammation that aggravates diabetes, heart disease and other health conditions.

People with lung or heart disease, children and older adults are especially at risk for smoke-related illness. The NWS advises people avoid smoke by limiting outdoor activities and keeping windows closed overnight.

Smoke seasons are getting worse

In the US, the window for outbreaks of unhealthy wildfire smoke is getting bigger, as fire seasons in the West have become longer and more extreme.

Climate change was found to be responsible for the majority of the increase of surface wildfire smoke. This smoke has eroded decades of air quality improvements in parts of the US, particularly in the West.

Canada’s record-breaking smoke event was so far-reaching, a study from last year estimates more than 350 million people were exposed to daily wildfire smoke-induced air pollution.

Planet-warming pollution caused approximately 15,000 more deaths in the US from wildfire particulate matter from 2006 to 2020 than would have otherwise occurred in a cooler world, a study published last year found.

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