Happy perihelion!

Earth will be a perihelion, the closest point to the Sun, early Wednesday morning, January 4, 2023. The closest point, aphelion, will be on July 4.

So why are temperatures colder for us when the Earth is at its furthest from the Sun?

The Earth's orbit around the Sun isn't circular, but it is also not that far off. The 3.1 million mile difference between perihelion and aphelion seems huge until you realize that this is only about a 3 or 4% variation.

Seasons aren't caused by proximity. They are caused by the 23.5º tilt of the Earth's axis

Half the year the North Pole is more pointed toward the Sun providing more direct sunlight to the Northern Hemisphere, the other half the year it's the South Pole providing more direct sunlight to the Southern Hemisphere.

But those 3.1 million miles make some difference, don't there? Are South American summers hotter than North American ones, especially around perihelion?

No. The tiny amount of extra solar energy received is quickly soaked up by the oceans. There's a lot more ocean in the Southern Hemisphere than the north. While about 60% of the Northern Hemisphere is covered by water, about 80% of the Southern Hemisphere is covered by vast, deep oceans, which don't absorb heat as well as land.

You can see Mars, another planet with seasons because of it's very Earth-like axial tilt of 25º, tonight high in the south eastern sky.  Continue to look throughout the evening and you''ll see Mars wind its way clockwise around the Moon.  That apparant movement is being caused in large part by our axial tilt.