If you're in the northern hemisphere, then you are currently experiencing late fall/early winter type weather. But why do we even have seasons? And why is it warmer near the equator in winter than it is at the poles? The answer is because Earth is tilted!
Most astronomical pictures project Earth as an "upright" body, with the north celestial pole at the top and the south celestial pole at the bottom. But actually, Earth is tilted 23.44 degrees from the poles being perpendicular to Earth's orbit. Earth's orbit around the sun is almost a perfect circle, so if the Earth was upright, it would be very hot at the equator, very cold at the poles, and every day and night would have exactly the same length. But since the Earth is tilted, we experience seasons. Let's look at the image above. Currently, the Earth is just about at the far left position on the diagram. This is how the Earth appears during winter for the northern hemisphere, and summer for the southern hemisphere. Because the north is tilted away from the sun, it's receiving less direct sunlight and is therefore colder. The south is currently angled towards to sun and receiving more direct sunlight, so it's warmer. As the Earth orbits the sun counterclockwise, we reach northern spring and southern fall, a point where neither hemisphere is angled more towards the sun. This is what gives us our intermediate seasons. On the far right, it's northern summer and southern winter, for the same reasons discussed previously, only now the north receives more direct sunlight. Temperatures at the equator don't fluctuate much at all, because the angle at which it faces the sun doesn't change much. So if you are currently freezing cold in the snow, or basking in the sunlight, you have Earth's tilt to thank or blame!
