The key may lie in the phrase "unslakeable thirsting in the backyard" in the last verse. (Yes, "unslakeable, " as in "insatiable, " one example of Veirs' idiosyncratic use of language.) She's not crass enough to spell it out so explicitly, but she's equating emotional longing with heat-wave dehydration, in a wonderfully subtle way.

NPR: Laura Veirs: Thoughts Of Summertime