Eventually it cooled off enough that I could get the last of the planting done: two white bleeding hearts, one in the woodland garden and one in the white garden.
EDIT 6/12/17: After supper, we went out and moved four small piles of grass. It is still hot but no longer unbearable.
EDIT 6/12/17: I went out and watered plants. As it's now dusk, I am done for the night.