What is the first day of summer?
Astronomical summer in the northern hemisphere begins at the June solstice, the moment the sun reaches its highest point in the sky and the longest day of the year. The exact instant falls on 20 or 21 June depending on the year and your zone, so this countdown uses 20 June as an approximation. Meteorological summer starts on 1 June instead. South of the equator the same solstice marks the shortest day and the start of winter.
The next one falls on Sunday, 20 June 2027, and this page counts down to the midnight that starts it in whatever time zone your browser reports. For a date of your own, the deadline countdown takes any target and tracks progress against it.