Here's why:

* Earth's Tilt: The Earth is tilted on its axis. This tilt causes different parts of the Earth to receive more direct sunlight at different times of the year.

* Summer Solstice: During the summer solstice (around June 21st in the Northern Hemisphere), the Earth's tilt is such that the Northern Hemisphere is tilted most directly towards the sun. This means the sun appears higher in the sky and stays above the horizon for longer.

* Longer Days: The higher sun angle also means longer days and shorter nights in summer.

Let me know if you have any other questions!