Not necessarily. Rawlings Conservatory is all under roof. It poured rain the whole time we were there, but the light was gorgeous. By the time Scott and I had driven up to Clyburn Arboretum after lunch, the rain had stopped and there was a beautiful fog. I can't go this weekend, but if I were I'd pray for bad weather so that I can photograph in such beautiful light.
At this time the forecast calls for "occasional showers possible-highs in the mid-60s".