Summer Solstice 2025 Northern Hemisphere Events. The northern hemisphere will mark the summer solstice on 21 june, the ‘longest day of the year’, when there will be around 16.5 hours of daylight. Is it really the longest day of the year?
When is the summer solstice in 2025? This is the first day of summer (summer solstice) in the northern hemisphere and the first day of winter (winter solstice) in the southern hemisphere.