Why do stars seem brighter in winter?

"As seen during Northern Hemisphere winter (or Southern Hemisphere summer), the stars seem brighter. Why? It’s because – on December, January and February evenings – the part of Earth you’re standing on is facing into the spiral arm of the galaxy to which our sun belongs.

From Images 108

Consider the sky at the opposite time of year. In June, July and August, the evening sky seen from the entire Earth is facing toward the center of the Milky Way galaxy. The galaxy is about 100,000 light-years across, and its center is some 25,000 to 28,000 light-years away. We don’t see into the exact center of the Milky Way, because it’s obscured by galactic dust. But during those Northern Hemisphere summer months (Southern Hemisphere winter months), as we peer edgewise into the galaxy’s disk, we’re gazing across some 75,000 light-years of star-packed space (the distance between us and the center, plus the distance beyond the center to the other side of the galaxy). Thus, at that time of year, we’re looking toward the combined light of billions upon billions of stars." ~EarthSky
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