Summer solstice marks the beginning of the astronomical summer season. Every year, the summer solstice occurs in June in the Northern Hemisphere, and in December in the Southern Hemisphere. 


In meteorology, June 1 marks the first day of summer in the Northern Hemisphere. The summer solstice is also the astronomical end of spring. Ancient cultures built monuments such as Stonehenge in England and at Machu Picchu in Peru to follow the Sun's yearly progress. People living in the Northern Hemisphere will witness early dawns and late sunsets, and the high arc of the Sun across the sky each day. 


At What Time Does Summer Solstice Fall This Year?


This year, the summer solstice falls on Tuesday, June 21, at 9:14 UTC (2:44 pm IST) in the Northern Hemisphere. On the summer solstice, the Sun appears highest in the sky for the year, and a full Moon near the summer solstice appears low in the sky. 


Since the summer solstice occurs in June in the Northern Hemisphere, it is known as June Solstice. Meanwhile, the summer solstice occurs in December in the Southern Hemisphere, and hence, is known as December Solstice in the regions located south of the equator. 


For people living in the Northern Hemisphere, the summer solstice marks the longest day and the shortest night of the year. 


After the summer solstice, the Sun will be moving south again. A solar day, which is the time it takes for the Earth to rotate about its axis so that the Sun appears in the same position in the sky, is longer than 24 hours near the solstice, according to NASA. 


Is The Longest Day Of The Year Also The Hottest?


Despite the fact that June Solstice is the longest day of the year for those living in the Northern Hemisphere, it is not the hottest day of the year. Instead, the Northern Hemisphere witnesses the hottest weather in late July and August.


This is due to an effect called lag of the seasons, according to EarthSky. Lag of the seasons is the same reason it is hotter in mid-afternoon than at noon. After a long winter, it takes the Earth some time to warm up. Ice and snow blanket the ground in some places of Earth, even in the month of June. It is only after the Sun melts the ice and warms the oceans that we feel the most sweltering summer heat. 


Though ice and snow have been melting since spring began, and meltwater and rainwater have been percolating down through the snow at the top of glaciers, the runoff from the glaciers is not as great now as it will be in July. 


As a result, the Northern Hemisphere will witness the hottest weather in July or August, a time when the days begin to shorten again. 


The Science Behind Summer Solstice


Earth has seasons because the planet's imaginary axis is tilted. The northern summer solstice is an instant in time when the north pole of the Earth points more directly toward the Sun than at any other time of the year, marking the beginning of the astronomical summer season in the Northern Hemisphere and the astronomical winter season in the Southern Hemisphere.


Therefore, all locations north of the equator will see days longer than 12 hours and all locations south of the equator will see days shorter than 12 hours.