The answer lies in the tilt of the earth on its axis. When the earth spins, it doesn’t do so along a vertical axis. Instead, it is tilted 23.5 degrees, and the tilt is always in the same direction. As we speed along on our 365 day trip around the sun, the northern hemisphere is tilted away from the sun in the winter months which gives us shorter days, which in turn gives us less sunlight each day to warm up the atmosphere.

The tilt also causes what sunlight does make its way to our neck of the woods to strike the planet at an angle, resulting in much of it being reflected back into space instead of being absorbed. Of course when it’s winter up here, it’s summertime in the southern hemisphere as that half of the planet is tilted towards the sun.