The tilt of Earth’s axis and the position on its orbit around the sun due to the rotation on the axis are the properties that cause seasons, according to the National Weather Service. Seasons are opposite one another on the Northern Hemisphere and Southern Hemisphere.
When the axis of the Earth leans toward the sun, it is summer for that part of the planet. At the same, the area of Earth on the axis pointing away from the sun experiences winter. For instance, when it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere. The Earth sits at a 90-degree angle at each equinox.