What makes a good sunset? Laura Kanofsky, a meteorologist with the National Weather Service office in St. Louis, said a pretty sunset can be a result of either a very clear sky or a very colorful sky, depending on people's taste.

A clear sky, so the viewer can see the sun on the horizon as it sets, would be the result of an arctic air mass. For dramatic sunsets with a lot of color, a viewer would hope for a cloudier sky. As the sun moves, the light illuminates the cloud layers in different ways, creating a range of colors.

If the atmosphere has a lot of the right type of particles (such as smoke from a wildfire), the sunset can be very colorful as the particles catch and diffuse the sunlight, Kanofsky said. Particles from pollution don't create this effect, she said.