Start Of Summer 2024. Here's everything you need to know about the northern hemisphere's longest day of the year. The first day of summer is also known as the summer solstice, and in 2024 it happens on thursday, june 20 at 4:51 p.m.

The summer solstice marks the first day of summer. In 2024, the summer solstice will occur at 4:50 p.m.