I've been diving the last two weeks in just a skin, and although I get cold the last 15 min of a dive, not enough to make me wear more. My computer has been saying 80. I've been diving here other parts of the year and have always only used my licra skin. I would rather travel light, and I can always borrow a shorty from a dive shop if needed.
Even when vis isn't great due to high wind as Harriette mentioned, it's still 50-ish ft. And once wind dies down, back to 80ish.