What temperatures can flat panel t.v.'s be operated at?
I live in Minnesota and need to replace the t.v. in my garage.

Apparently you are not alone: LCD TV in Cold Weather - The Garage Journal Board

I believe Plasma's can only be used to a certain Altitude?

Just found this:
How Altitude Affects Plasma TVs

I guess they can be used, just maybe noisey?

Placing just about any TV in such an environment will void the warranty, and in most cases will also void any extended warranty.

That being said, there used to be flat panel TVs that were made for all weather rooms/outdoors. I'm not sure if there are still these TVs as a few years ago, they were pretty expensive and as such didn't sell extremely well.