When Memorial Day was given the designation of the unofficial beginning of summer, meteorologists were clearly not consulted!
Astronomical Summer
Astronomically speaking, summer is roughly from June 21 through September 20, and it’s based on the position of the sun in the sky. While that, technically, has nothing to do with the weather, the weather is a reflection of the position of the sun. When the sun is aimed more at the northern hemisphere–as it is from June 21 through September 20–it will be warmer in that hemisphere. In other words, it’ll be summer. You don’t need a four-year degree to figure that one out.
Meteorological Summer
Meteorologically speaking, summer as the warmest three-month period of the year, which, for most areas, is June through August. That, however, is an oversimplification.
Unbalanced Seasons
It’s hard to imagine that September in the Deep South, where it’s typically hot and humid day after day, is no longer summer, and it’s hard to imagine in the Desert Southwest that May, when temperatures often exceed 100 degrees, is spring.
There are also some locations, such as coastal areas of California, including San Francisco, where the average high temperatures peak later in the season–it’s warmer in October than in July. (This late-season warmth is related to the gradual moderation of ocean water temperatures and the increasing likelihood of a warming offshore flow.)
According to my wife’s definition, summer in Pennsylvania is about two months long, and when snow flies in April and highs in September are in the 70s, it’s hard to argue with her–not that I ever would.
–Paul Yeager
