When Is Summer 2025 Uk Start Date. In 2025, these are the astronomical dates and times for the start of each season: Find out the date when summer is in 2025 and count down the days until summer with a countdown timer.

The end of summer is marked by the september equinox, which signals the arrival of fall/autumn. This is the first day of astronomical summer and occurs as the sun reaches its most northerly or southerly path in the sky.