The way the hemispheres and earths axis faces the sun changes so when the Southern Hemisphere is closer to the sun the northern hemisphere is further away as in getting colder
Earth's tilted axis causes the seasons. Throughout the year, different parts of Earth receive the Sun's most direct rays. So, when the North Pole tilts toward the Sun, it's summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it's winter in the Northern Hemisphere.
