It was silly but apparently I was waiting for the heat to break so that I could feel better. With my brain on molasses mode it took days [and days] for me to realize:
a] not exercising was making me feel really crappy [and crabby]
b] perhaps it would be useful to figure out a way to exercise in spite of the heat thus feeling better sooner
It took awhile but finally I gave up on the expectation 'summer = exercising outside' and headed indoors to the Y and started running there.
Much better. It makes me giggle to think of my slowness.