Summer provides the warmest weather of the four seasons as the days become hot and often dry (rainy in some Asian areas) with evenings remaining warm to hot depending on your location. In the Northern Hemisphere summer comes in the June, July and August months and in the Southern Hemisphere it comes in the December, January and February months. Summer comes about by the Earth increasing its axis tilt relative to the sun till the Summer Solstice (June 20-22 in Northern Hemisphere) then the sun relative to the earth changes course and starts to move back towards the equator.
During the Summer solstice the sun shines directly on the Tropic of Cancer in the Northern Hemisphere and the Tropic of Capricorn in the Southern Hemisphere and the day is longest with nights the shortest. As the summer season progresses from its start around June 20th to 22nd (June Solstice - Northern Hemisphere) with the sun overhead the Tropic of Cancer, it changes course and begins to move back toward the equator. In the Southern Hemisphere the sun moves on December 20th to 23rd (December Solstice) from its overhead position on the Tropic of Capricorn, changing its course and moves back toward the equator.