Occasionally moments, the sun can appear to be a bright or deep red color, rather than the more common shades of yellow. The color of the sky or the sun may be in part due to factors of climate change, and can be jarring to see. So why does the sun look red at times?
A late-May 2023 occurrence of a bright red sun, as seen from a number of states in the U.S., is being attributed to wildfires in Canda. Outdoor conditions play a large role in how dark the night sky is as well as the color of the sun. Here's how outdoor conditions play a role in the way the sun looks to the human eye.
The appearance of a red sun is often due to wildfires.
Why does the sun look red on certain occasions? The phenomenon is often attributed to the presence of wildfires that add smoke to the atmosphere. For example, late in May of 2023, residents of Illinois, Iowa, New York, and New Jersey were among those who saw the sun looking red, as The Daily Mail reported. The outlet noted that although the photos could be gorgeous, it was not a good sign.
The Daily Mail said that the bright red colored sun looked that way due to about 84 wildfires burning in Canada, and that smoke traveled up to 2,000 miles to create a "hazy filter over the sun, making it appear fire engine red." The smoke filters out shorter wavelengths of light and allows the red and orange wavelengths to shine more brightly.
Meteorologists have said that jet streams blow smoke particles across the U.S. into northeastern regions, which impacts air quality as well as causing the bright red hue of the sun as seen from those regions. The sun can also look dimmer due to smoke coming from Canada, said The Daily Mail.
The Canadian wildfires have led to poor air quality in parts of the U.S.
As Axios reported, due to these Canadian wildfires, several U.S. states issued air quality alerts, including Colorado, Utah, Montana, and Idaho. In Montana, the National Weather Service advised those with respiratory illnesses to stay indoors. Similarly, Utah's Department of Environmental Quality said air quality would be "unhealthy for sensitive groups."
Sunrise and sunset are also more likely to display a red sun.
The sun is often found to have more of a reddish color around sunrise or sunset, even without the presence of wildfires. As Met Office, the U.K.'s meteorological service, explains, at sunset the light from the sun must travel further through the atmosphere than during the day. The atmosphere scatters blue light more strongly than red and yellow light, so at sunset the red becomes more visible to us on Earth.
So while a reddish-looking sun can happen at sunrise or sunset, some of the most dramatic red suns are due to wildfires and the associated smoke from those wildfires. These fires aren't just a coincidence, though. Climate change leads to more frequent wildfires; warmer and drier conditions, drought, and and longer fire season all increase that risk, as the Center for Climate and Energy Solutions explains.