I need to get my butt in gear

I'm heading up to Toronto tomorrow morning, but I still haven't finished packing. I took a peak at the weather and it says it's supposed to be around 20 degrees for the next couple of days. I'm excited that it's supposed to be niceish weather on my days off, but I have no idea what clothes to pack! Do I bring jeans? Shorts? A dress?

Ugg.