First Day Of Summer 2024. Usually, when we talk about the first day of summer, we are referring to the astronomical summer which is defined by the earth's axis and orbit around the sun. In 2024, the summer solstice will occur on june 20, at 20:51 gmt in the northern hemisphere, and on december 21, at 09:20 gmt in the southern hemisphere.
Today (june 20) the summer solstice โ the longest day of the year in the northern hemisphere โ will begin, and it will be the earliest solstice in 228 years. When is the first day of summer in 2024?