weather in atlanta?

I have a question. Does anyone know what the weather is likely to be in Atlanta, Georgia, at this time of year? That is: what do I need to pack? I'll also be indoors at a hotel conference centre thingy for much of the time: is that likely to be overheated? airconditioned? freezing cold? Do I need to take a brolly?

Much appreciated!

*buries head back in conference paper*