Why is the insolation for January and July nearly opposite from each other?

Insolation, or incoming solar radiation, varies with the Earth's tilt on its axis and its orbit around the Sun. In January, the Northern Hemisphere is tilted away from the Sun, resulting in lower insolation and colder temperatures. Conversely, in July, the Northern Hemisphere is tilted toward the Sun, leading to higher insolation and warmer temperatures. This seasonal variation is reversed in the Southern Hemisphere, where January corresponds to summer and July to winter.