I believe the OP meant 80 degrees would be the high of the day, not that the temp would go to the high 80s.
But I agree with you, once we got off the plane and it was upper 80 or so and we felt awful after a short while. We now carry a pair of shorts in our carryon .
But back to the question....I don't think we could do it, with just t shirt and jacket tied around waist. But since DH uses a wheelchair at disney now, so we would probably add a thin long sleeve and a hat , along with the jackets and tote them with the chair.