Wildfires in Canada turned New England skies yellow this week, prompting officials to warn sensitive groups and raise air quality alerts, which remain in effect for Fairfield, New Haven, Middlesex and New London counties until Thursday night.
The eerie glow may have reminded you of 2023 when wildfires in Quebec caused skies across the Northeast to turn bright orange.
If you want to know why bad weather turns the sky different colors, think back to your middle school science class where you might have learned that white light is actually made up of all the colors you see in a rainbow.
“If you put light through a prism or if you look up at a rainbow, you see a lot of different colors and those colors range all the way from red and orange down to indigo and violet,” said Connecticut Public’s chief meteorologist, Garett Argianas.
During a wildfire, particles in the air, like ash and smoke, absorb colors with shorter wavelengths, which are on the blue and violet end of the spectrum. That leaves colors with longer wavelengths — like yellow, orange and red — passing through.
The intensity of the color is related to the thickness of the smoke, its density and the size of the smoke particles, according to Argianas.
“The greater the impact of the smoke, the more oranges and reds we see,” he said.
Connecticut's Department of Energy and Environmental Protection urges children, the elderly and those with pre-existing health concerns like asthma, lung or heart problems to limit time outside and keep an eye on coughing and shortness of breath.
If you plan on running your air conditioner, you can reduce your exposure to ash and smoke particles by putting it on recirculate or fan mode, or you can use an air purifier.
Eyes to the skies
Sepia-toned skies from wildfire smoke are similar to what happens when the sky turns green during tornadoes and thunderstorms, according to Argianas.
“In the case around tornadoes, it's more about water in the air absorbing different wavelengths of light,” he said.
“There's often hail in the mix as well.”
In fact, green clouds could indicate that hail is nearby, according to the National Oceanic and Atmospheric Administration, although scientists don't always agree on why exactly the sky turns green during severe weather.
“One theory is that large amounts of water and ice in the updrafts of a severe thunderstorm will scatter green light, making the clouds appear green,” according to NOAA’s Severe Storms Laboratory.
Áine Pennello is a Report for America corps member, covering the environment and climate change for Connecticut Public
