Our recent stretch of sunny days has prompted many people to comment to me about how beautiful the sky is this time of year. In some ways, the fall foliage show each year is spectacular not only because of the array of different colored leaves, but also because of the sharp crisp blue backdrop that enhances the view.
The autumn sky tends to look sharper and bluer this time of year for a couple of reasons. During the summer, the dew point temperature tends to be much higher and this extra moisture makes the atmosphere hazy, giving the blue sky a dull, milky white appearance. In the fall the moisture content in the air is much lower giving the sky a deeper blue appearance, especially when contrasted to what was seen all summer.
Plus, the lower sun angle this time of year enhances the scattering effect of the blue wavelengths that give the sky that classic autumn blue color.