how to pack snakes in summer?

[crocsnhots]

Hey everyone,
I have 9 snakes I want to sell and ship out, but before I advertise them, I wanted to know, how do I pack them for summer shipping? Do I need to put some sort of cool pack in with them? If so, what type?

I've never shipped before, I've recieved stuff numerous times but they were always during the cold months where heat packs were in use. I know how to pack the snakes up in a styrofoam lined box, and make sure the snakes can't be bumped around too much, but I'm not sure how I should go about this summer shipping.

Any help and advice greatly appreciated.
Thanks