Quote:
Originally Posted by GeoffC
Sorry, it must be my background showing, summer extends for the whole months of June, July and August in the northern hemisphere ....
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For us (Florence and your humble servant) it goes with the nodes of the Earth trajectory. Solstices and equinoxes. Roughly the 21st of December, March, June and September.
Or maybe with the stationary points of the yearly plot of daylight. Maximum and minimum for solstices. Stationary derivative for equinoxes.
In astronomical reckoning, the solstices and equinoxes ought to be the middle of the respective seasons, but,
because of thermal lag, regions with a continental climate often consider these four dates to be the start of the seasons as in the diagram, with the cross-quarter days considered seasonal midpoints. The length of these seasons is not uniform because of the elliptical orbit of the earth and its different speeds along that orbit.