It's an interesting and little known fact that the Earth is actually at it's closest point in relation to the sun in January on our calendars. I know, I know, I can hear you already, it doesn't make sense that the weather for us is coldest when we are closest to the sun. Well here's the explanation. Most people don't realize that the Earth is tilted on an axis of 23.5 degrees. It is that fact in conjunction with our atmosphere that causes the weather to be coldest when we are closest to the sun. First, during northern hemisphere(that's where we live)winter, we are tilted away from the sun. So the sun's rays hit our atmosphere at more of an angle, and are more diffused by the atmosphere by time they get to us. During northern hemisphere summer we are tilted closer to the sun, and the suns rays hit us more directly, if you notice the sun seems more "directly" overhead during the summer. When January comes, we get closer to the sun, but the 23.5 degree tilt points us away from the sun, and the atmosphere diffuses the incoming light and spreads it over a wider area, making it weaker, and the temperatures colder.
To see this effect for yourself, take a flashlight, and point it at a spot on the wall directly in front of you. You will see the light makes a nice even circle that is very bright. Now take a couple of steps to the left or the right, and keep the flashlight pointed at the same spot on the wall. You will notice the area of light gets bigger, more oval shaped, but it also gets dimmer. A larger area is lit, but less powerfully. That effect is exactly what happens to sunlight coming in contact with the earth. Hence forth, the winter and summer seasons.
