Summer 2025 Start Date. Online calendar of holidays and days off in united states for the summer of 2025. When is summer in 2025?

Summer 2025 starts on friday, 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 having reached its furthest tilt and begins to change directiion back. In 2022, summer started on tuesday, june 21.