Seattle sunsets are red this week, due to a thick blanket of smoke from Canadian wildfires. More than 500 fires are burning in British Columbia, prompting a state of emergency that is expected to last two weeks.

In Northern California, the Mendocino Complex fire is the largest in the state's history. The network of nearby wildfires in the middle of the Golden State has burned more than 360,000 acres — an area 4½ times larger than Philadelphia. As of Thursday, the blazes were still growing.

The colossal fires on the West Coast are now impacting the air flowing into Pennsylvania, according to the National Weather Service.

"The sky yesterday in our area had a milky appearance to it, which typically occurs when there is smoke present," said Michael Gorse, spokesperson at the service's Mount Holly office.

The Western fires are producing "tremendous" amounts of smoke over an "enormous" section of North America, according to the most recent satellite imagery report by the National Oceanic and Atmospheric Administration. Smoke has spilled out over the Pacific and Atlantic Oceans, with only the southern belly of the country unaffected.

The jet stream, which blows from west to east, is stretching the smoke across the American heartland at a high altitude. In the Philadelphia area, most of the smoke is staying far overhead – more than three miles above the Earth's surface, said Sarah Johnson, a meteorologist at the Mount Holly office.

It is "not uncommon" for Western smoke to travel thousands of miles to reach the Eastern seaboard, she said.

In other areas on the East Coast, the smoke has dipped to ground level. The Washington Post reported Thursday that residents in the Baltimore and Washington areas were smelling wildfire smoke.

Air quality in the Philadelphia region is not being affected by the smoke, said Johnson, though "locally driven" weather systems are producing a moderate, or yellow, air quality index, which is generally considered acceptable.

The red hue of sunrises in the Philadelphia region the last couple mornings was due in part to scattering of light by the smoke, Johnson said.

As climate change drives up the intensity and duration of wildfires, we all may have more crimson mornings.