Why is it usually hotter in the middle of the day? Why is it almost always cold in the north and south poles, and almost always hot near the equator?
There are lots of things that can affect what the temperature is in a certain place, but one of the main ones is latitude. Latitude is a number that says how far north or south of the equator you are. If you are in a pretty cold place like Trømso, Norway which is very far north, or Patagonia, Argentina, which is very far south, then you are in a "high" latitude. If you are in a pretty warm place, like Hawai'i, which is close to the equator, you are in a "low" latitude.
So, what is it about going closer to the equator that makes a place hot? Is it that you get closer to the sun when you go closer to the equator? Well, it's true that you might be a teeny-tiny-bit closer to the sun when you are on the equator, but we are already so many millions of miles away from the sun that it really doesn't make a difference.
What makes a difference is the angle between the ground and the sun's rays. The sun's energy comes to us in "rays" - big invisible waves of light and heat. Those invisible rays are always coming out of the sun and coming toward us. The energy coming from the sun is just about the same everywhere, but if the angle makes it come "straight down" then that same energy is focused on a smaller spot. If the angle of the ground is "tipped away", like it is in the higher latitudes, then that same amount of heat energy is getting spread out over a larger amount of space. It doesn't heat up the area as much because it's the same amount of heat but a bigger amount of space.
Can you think of other things that might be caused by the angle of light coming to earth? What else makes temperature change besides "where" you are? What changes each year?