Are they gonna freeze???

As you know I am an indoor Gardener. This year I have been trying some outdoor experiments.
They seem to be doing very well for seeds that were popped in mid june.
My question is at what temp (low) will the plants start having problems, Now obviously I am talking about temp above freezing. I do know if they freeze its over (so I have been told). What I am wondering is how will the cold affect the plants?
I live in the southwest so I get the worst of the growing enviorment's.
Super hot days, and very crisp cold nights.

Can a plant sense the freeze coming? Will they speed up there finish or just wait to freeze?
They are all in aggressive flower as of now. So things are moving along very nice, I was wondering if there was any potholes I should be looking for in the future.
I will say that it is different going from little indoor plants to the monsters I have to deal with outside.

If I get any comments I will post some pics.
Thanks for the help.
DMG

it was only +3 Celsius this morning,with light frost.i put my plants in a hide at night but there was still frost on the ground,so it was pretty cold but the plants dont mind,as long as they dont get frost on them they will be ok.maybe cover them with a sheet or tarp at night.

Do you think it is the actual frost that does the deed?
The freezing on the leaf surface would cause necrosis?
What about ambient air temp, I am no where near your temps.
Right on.

i think you'll be ok as long as the air temp doesn't go below 0 c