Start And End Of Summer 2025. When is the first day of summer 2025. Summer 2025 starts on thursday, june 20th in the northern hemisphere, with the first day of summer being the longest daylight day of the year with the earth's axis.
In north america, summer officially begins on thursday, june 20. Summer 2025 starts on thursday, june 20th in the northern hemisphere, with the first day of summer being the longest daylight day of the year with the earth’s axis.