The Earth's axial tilt is what causes seasons, and this tilt remains constant at 23.5 degrees throughout the year. This means the Earth is tilted at 23.5 degrees in winter as well as in summer.

However, the angle of the Earth relative to the sun changes throughout the year, and this is what causes the differences in seasons. During winter in the Northern Hemisphere, the Northern Hemisphere is tilted away from the sun, resulting in shorter days and colder temperatures.

So, while the Earth's axial tilt remains constant, the angle at which sunlight hits the Earth changes throughout the year, leading to the experience of different seasons.