Neptune's seasons. Image 3 of 3. Hubble Space Telescope image of cloud bands on Neptune in 2002. Large white and green cloud bands are seen in the south, which could be due to the arrival of spring. Seasons on Earth are caused by its axial tilt of 23 degrees, meaning that the hemispheres receive different amounts of light at different times of the year. Neptune has an axial tilt of 29 degrees, so a similar effect could occur. One year on Neptune is 165 Earth years, so the seasonal change would be correspondingly slower. For a sequence of the clouds brightening and enlarging over six years, see images R420/087-089.