Wildfire smoke now covers much of the United States, turning skies gray and the sun red

The AirNow fire and smoke map shows a film of gray wildfire smoke across most of the US on July 20, 2021.

AirNow

I've been noticing strange sunsets lately in New Mexico where the sun looks like a molten ball of red as it sinks into the west. It's one symptom of wildfire smoke in the sky and a sign of another brutal wildfire season in the US.

The National Weather Service office in Aberdeen, South Dakota, tweeted on Tuesday: "You've probably noticed the persistent hazy skies as of late. Turns out we're not the only ones seeing this -- smoke from wildfires is covering much of the lower 48."

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Get the latest science stories from CNET every week. Besides apocalyptic-looking sunsets and orange skies, wildfire smoke can impact air quality far from where a fire is actually located. The wildfires, many of which are burning in the western US, have been fed by severe drought conditions and heat waves.

These events have been exacerbated by the climate crisis and the extreme weather it brings with it. The National Weather Service shared a fire and smoke map from the AirNow air quality monitoring site. What's notable are the wide swaths of gray indicating smoke coverage over the US and Canada, as well as the many marked wildfire locations, denoted by the orange fire icons.

Oregon's massive Bootleg fire is one example of just how bad the 2021 wildfire season is.

The fire has burned hundreds of thousands of acres and sent huge amounts of smoke into the air. It is only 30% contained. The National Oceanic and Atmospheric Administration shared a time-lapse look at wildfire smoke spreading from July 15 to 19.

The images come from the GOES-East weather satellite. The grayish haze stands out from the white clouds.

The smoke may linger for some time. According to the National Interagency Fire Center's Tuesday report, "Wildfire activity continues in 13 states where 83 large fires have burned 1,293,636 acres." Many wildfires are caused by humans, but lightning strikes are another major trigger, particularly in remote regions. This year's smoke-filled skies may feel like deja vu after a devastating year in 2020.

If you live in an area where wildfires are a possibility, check out our preparedness guide.