The seasons occur because Earth tilts (specifically at 23.5 degrees) during certain months. For example, in June, the summer solstice happens (or summer), where the days are longer and the nights are shorter. In september, the winter solstice happens (yes, winter), where the days are shorter and nights are longer. In the spring and fall equinox (where spring and fall occurs), the day and nights are even-- 12 hours daylight, 12 hours night-time.