With 8 inches of hail falling in parts of Nebraska this week and Arizona reaching triple digit temperatures last week, it may seem rather arbitrary to call June 20 the first day of the summer this year, aka the summer solstice. But scientists really do have a reason.
It's all about Earth's cockeyed leanings and some celestial configurations that even the ancients understood.
Our planet is tilted 23.5 degrees on its spin axis. On June 20 this year (some years it's June 21), the North Pole is pointing toward the sun as much as is possible.