Why are Winter Sunsets Just … Better?

Did you know that sunsets are actually better in the winter? It's all science! Humidity is lower in the winter, and the air is cleaner. That causes purer colors to be splashed across the Northern Hemisphere’s skies. 

First, some basics. The vibrant colors humans see in sunsets are caused by the same process that makes our daytime skies look blue. It’s called Rayleigh scattering. That is when sunlight bounces off of air molecules. 

Sunlight has all the colors of the rainbow. Each color is a wavelength of light we can see. But we don’t always see them all, though. That’s because Rayleigh scattering impacts shorter and longer wavelengths in different ways. So, they reach Earth in different amounts at different times. 

During the day, we see the sky as blue because molecules in the air scatter the shortest visible wavelengths of light the most. Those look blue and violet. These wavelengths bounce around in the atmosphere, where we see them. Longer wavelengths of light travel to Earth. We don't see those.    

Each evening, the sun being closer to the horizon as it sets means light travels farther to reach our eyes. By the time it reaches us, blue light has already been “scattered out.” This leaves the longest wavelengths (red and orange) to bring us those glorious “blazing” or “fiery” sunsets.

The wintertime wow factor is that colder air is generally less humid. So, there’s less water for the tiny particles in air to absorb. Fewer water-filled particles mean less light being scattered. As a result, the colors look bolder. The air that wavelengths travel through in winter is also generally cleaner. That's because much of the air is blown from the Arctic. There isn't much air pollution there. 

Photo by Tobias Mockenhaupt courtesy of Unsplash.