• For some it is Memorial Day weekend.
• some it is when school gets out.
• for meteorological summer in Minnesota June 1st is the date normally used.
• For astronomical summer it goes by the day with the longest daylight
  (Summer solstice)
• in Northern Hemisphere is June 20 2017
• in Southern Hemisphere it is December 21 2017
• Have a Happy Summer

more about seasons: https://www.ncei.noaa.gov/news/meteorological-versus-astronomical-seasons