Summer Begins At The Summer Soltise? Or does it?
My calendars all say so.
Then why is it called Mid-Summers Day? :rolleyes:
I’ve done some research on this subject, and the result seems to be: Nobody’s quite sure when to peg the ‘changing’ of the seasons, despite the fact that we all use the terms summer, winter, spring, and either autumn or fall. (Well, everyone in english-speaking countries north of the equator I believe.)
First off, about the solstices and equinoxes. The Summer solstice is the point in time (or the day surrounding it,) when the northern hemisphere is ‘pointing’ most directly towards the sun, thereby getting the most heat and the longest days. The winter solstice is the point where we are point most nearly away from the sun, getting the least heat and the shortest days. (The southern hemisphere generally keeps these meanings to refer to their own orientation and therefore celebrate the opposite solstices as us at the same time IIRC)
The vernal, or ‘spring’ equinox is the moment where the sun ‘crosses’ and will begin spending more time north of the equator than south, and generally happens around march 21st. The autumnal equinox in september is the reverse, when the cross is from the northern hemisphere to the southern.
Now, let’s look at the question of when summer begins and ends. Generally, the term is understood to mean the season where air temperatures are at their warmest, days are long and sunny (except for sudden and intense thunderstorms, if the local climate calls for them.) Now, we in the northern hemisphere get the most sunlight and sun-heat in the three months surrounding the summer solstice… from may 6th through august 6th, roughly.
However, direct heating factor is not the only concern. Air, water, and ground also have a tendency to retain heat, so during may, for instance, a lot of the heat we get from the sun is still going towards killing the last of the winter chill, and it will generally not be as warm as, say, late august… even though the amount of heat from the sun is lower, everything is still retaining a lot of warmth and what energy that does arrive from the sun is just enough to keep things sweltering.
So… given that the ‘retention effect’ is vague and varies from place to place, (since ground and water retain in different ways, for instance, and different places have different amounts of water nearby,) where do we mark off the year into four different seasons? Some people seem to get the notion that we should push things back far enough that the solstice and equinox points should mark the changing of the seasons… spring goes from the vernal equinox to the summer solstice, summer goes from the solstice to the autumnal equinox, fall goes from the equinox to the winter solstice, and winter from the solstice back to march 21st.
I tend to hold that, if we’re picking arbitrary dates anyway, this goes a little too far with the retention effect, and go back to my grade school days where we split things up by months… march april and may are spring, june july and august are summer, september october and november are fall, december january and feburary are winter. 
There are other systems, but this would but the middle of summer around july 15th, and the beginning on june 1st.
YMMV
chrisk, well put.
Here’s what the Master had to say about the matter.http://www.straightdope.com/classics/a1_170b.html
ps
A quick Google turned up this interesting link