In meteorology for the Northern hemisphere, summer begins on June 01, 2018. It is also called the beginning of meteorological summer. The meteorological seasons are divided according to the calendar months. Summer months are June, July and August.
This meteorological definition of summer also aligns with the commonly viewed notion of summer as the season with the longest and warmest days of the year, in which daylight predominates. At the summer solstice, the days are longest and the nights are shortest, with day-length decreasing as the season progresses after the solstice.
Summer is traditionally associated with hot dry weather, but this does not occur in all regions. In areas of the tropics and subtropics, the wet season occurs during the summer. Schools and universities typically have a summer break to take advantage of the warmer weather and longer days. (With material from: Wikipedia)