The Washington PostDemocracy Dies in Darkness

This is why D.C.’s sunrises and sunsets have had a reddish hue

Sunrise and sunset this past weekend appeared more like a moonrise and moonset because of western wildfire smoke

Western wildfire smoke dimmed and scattered the light at sunrise on Sept. 18, which produced soft, reddish hues in the sky. The sun aligns with the Mall twice a year at sunrise and sunset, always occurring near the spring and fall equinox. (Kevin Ambrose)

The sun’s usually bright and vibrant colors at sunrise and sunset in recent days were replaced by dim and soft reddish hues in the sky. The culprit? Western wildfire smoke in the atmosphere that filtered the sunlight reaching the ground.

As a result of the smoky haze, sunrise and sunset appeared more like a moonrise and moonset — with lower contrast and more detail in the sun. Some images show sunspots that triggered recent aurora displays.

You may have noticed that the smoke was also less apparent during the midday. The sky was slightly less blue and had a milky-white appearance during much of the day. But at sunrise and sunset, the sun dramatically dimmed and appeared to become a soft glow in the sky near the horizon.

The enhanced reds of a smoky sunset are thanks to the short wavelengths of blue light being captured by the haze. Red or orange wavelengths are longer and able to pass through and be seen.

Photographing a smoke-dimmed sun in the sky is much easier than shooting an extremely bright sun. This is because the sun and foreground can be properly exposed in a photo with a dimmed sun. It is similar to the lower contrast that makes for pleasing “blue hour” images around dusk and dawn.

While wildfire smoke aloft in our skies has already significantly lessened compared to recent days, thanks to a weak cold front moving offshore, we may continue to see some until a stronger push of cooler air moves in from the north during the midweek.

Fortunately, an early-season storm will drop rain across the West Coast. While it has not fully extinguished the ongoing fires, more moisture in the region has helped firefighting efforts. The amount of smoke entering the atmosphere is currently much lower, which may help keep our skies cleaner ahead.

Many Capital Weather Gang readers and photographers in the area captured the smoky skies as well. Some of the best captures we have seen are included below.

Ian Livingston contributed to this report.