If you don’t know why we have seasons, here’s a great article on the explanation. It’s also notable that astrologically, each change comes about as the Sun ingresses a Cardinal Sign of the Tropical Zodiac, i.e. Aries, Cancer, Libra and Capricorn.
Some assume our planet’s changing distance from the sun causes the change in the seasons. That’s logical, but not the case, for Earth.
Source: Why Earth has 4 seasons