When is the first day of Summer?
Quick Answer: The first day of summer is the Summer Solstice, which usually falls on June 20 or 21 in the Northern Hemisphere.
The Summer Solstice marks the longest day of the year, when the sun reaches its highest point in the sky. This event signals the official start of summer.
Because Earth’s orbit isn’t perfectly aligned with our calendar, the exact date can shift slightly each year. In the Southern Hemisphere, summer begins around December 21 or 22, which is their Summer Solstice.