Well, you could have fooled me as it has been hot and like summer here for quite a while.
But, yes, technically, summer did not begin until today.
How do we know when it is summer?
What is the criteria for summer?
Well, this has to do with the equinoxes -- which we have previously referenced so you are probably experts on this by now.
But, just in case you are new to DITs (Daily Interesting Things) or need a refresher course, there are several sources of information about the equinoxes.
One of those sources is short, simple, and sweet in its explanation.
HERE'S THE LINK to understanding the equinoxes
