Cause of 24-Hour Daylight North of Arctic Circle at Summer Solstice

The midnight sun—24-hour daylight north of the Arctic Circle at summer solstice—results from three factors:

1. Earth's Axial Tilt (23.44°) – The axis is tilted relative to the orbital plane (ecliptic).
2. Orbital Position at June Solstice – The North Pole leans maximally toward the Sun.
3. Arctic Circle Definition (66.56°N) – The latitude where the Sun remains above/below horizon for 24 hrs at solstices.

Mechanism: At summer solstice (~June 21), the Northern Hemisphere is tilted toward the Sun. The Arctic Circle marks the southernmost latitude where the Sun's center stays above the horizon for a full 24-hour rotation. North of this line, the Sun circles the sky without setting. The effect lasts from one day (at the Circle) to six months (at the Pole).

Conversely, at winter solstice, the North Pole tilts away, causing polar night.