When It's Actually Winter...
That cover is not the right book, nor do I know why it pops up. Mine (rather, the library's) was authored by Dorothy Cameron Disney and George Sessions Perry. The library version just has green library rebinding with a nifty almost tropical pattern.
Of course I found it when they sent me to straighten the mystery shelves, though I've managed to avoid them for so long. But at least I didn't have to go far, only through the H section...otherwise my reading list would be even longer.
"When glittering Jenny Iverson, New York career woman and owner of a successful cosmetics business, invited herself to one of the labor Day week-end parties that climax the season for summer residents along the Connecticut shore, she not only wrote her own death warrant, but also sealed the fate of at least two other persons in the group of sophisticates who were to have shared her company during the holiday." 1942