yeast freezing

I had a quick question about the wyeast liquid yeast packets, specifically the activators. All it says on the wyeast site is that the packets contain a yeast slurry. I don't know what exactly they mean, obviously it is a packet of yeast in liquid, but is it water? (I should think it would be). So assuming it is water, my question is, is there a danger to yeast viability if the packet should be subjected to freezing temperatures? because I read that ice crystals damage yeast, so my concern is, having ordered a kit containing one of these yeast packets, should i be concerned that they it will probably sit on my porch for a few hours, when it is about 20 degrees here? Thanks in advance.

A few hours on the porch probably won't freeze the packet, but the slurry is water. Freezing would reduce viability, so I'd check the packets as soon as you can. Unless it is frozen solid, no worry. If it is, or if you'd like to be absolutely certain, just make a starter.

dont freeze them! Ice crystals can destroy the cell walls of your yeasties and leave you with a dead pack. You need to properly pack them with glycerin to avoid damage. Generally you would make a starter and save some to store in the freezer... check the "frozen yeast bank" thread in the general techniques forum for that.