First of all it sounds the space is not heated, so you're running out of time without auxiliary heat. You need to have the floor at 50 f.degrees or higher, that's 10 c., not just the air, but the concrete.
You should use a porcelain tile rated for outdoors and the appropriate thinset mortar for the installation system you select.
Originally Posted by nvstewar
So my question:
Do I need to consider plywood, backerboard or membrane on top of the concrete subfloor, or should I be o.k. tiling directly on it?
Definitely you can not consider plywood or backerboard on concrete, but a membrane would be smart. Ditra would be a good idea, or a liquid membrane at least.