what day does summer start

Summer can start on two different “days,” depending on which definition you use:

• Astronomical summer (used by most calendars and news sites) starts on the summer solstice , usually June 20 or 21 in the Northern Hemisphere, and December 21 or 22 in the Southern Hemisphere.

• Meteorological summer (used by climate scientists and many weather services) starts on June 1 in the Northern Hemisphere and December 1 in the Southern Hemisphere.

So when people ask “what day does summer start,” they usually mean the summer solstice in their hemisphere, but weather and climate data often treat the 1st of the month (June or December) as the start instead.