We were there the last week of March, 2007. It was definately sweatshirt weather. My older DS didn't swim at all, my younger DS only swam in the hot tub. The ocean water was freezing and it was really windy. We didn't have storms but the weather was definately not the highlight of the week.
We're back to the heat and humidity of summer next year.
If you do go in March, pack the bug spray. The no-see-ums/sand fleas were terrible.