Clean air! That's why Montana gets some doozies. Mild pollution is often stated as one of the factors in a brightly colored sunset but according to experts at NOAA that just isn't the case.

If that were true, China would be cranking out their own sunset calendars every year. Instead, we usually catch gorgeous sunsets on rural highways or in the tropics.

This quick, easy to read paper from NOAA on The Colors Of Sunset And Twilight is super interesting and explains a lot.