Most Helpful Girl
70 and below for perfect comfort, but I've worn sweaters in warmer weather1
Most Helpful Guy
In Florida, when the temp is 90 degrees F. or greater, the relative humidity is at least 80% and a sweater would represent a form of slow suicide. On the other hand, when the temperature is 15 degrees F. (and it does happen occasionally in North Florida,) it is usually either humid or windy or both, and a sweater would be woefully inadequate proptection against the elements.
In Florida, sweater weather would be roughly 45 degrees F. to 65 degrees F.1