Actually, the first day of summer is the day with the most hours of daylight due to one of Earth’s poles pointing most toward the Sun. This is called the summer solstice and it occurs around June 21 in the Northern Hemisphere. Earth is tilted at an angle of about. As it orbits the Sun throughout the year, Earth remains tilted. When Earth is at the point in its orbit where the North Pole is tilted most toward the Sun, the Northern Hemisphere experiences the first day of summer. On this day the Sun’s rays shine most directly on the Northern Hemisphere. It’s important to understand that the seasons are caused by the tilt of Earth’s axis, not the distance from the Sun.