Try it and see. I suggest keeping them below 90c at the very most, that might be hard even in a very cold room. I shoot for 75C on my miners, which can be hard to do.

For a short time (1-2 weeks) it may be OK, the cards are rated to 95c. The fans do not do well at temperatures like that, and will be the first thing to fail. Unfortunately, you'll just have to make a call. Is it worth the extra wear and tear on 2 cards for an extra 700kh/s for two weeks?

The cards should be OK running in a really cold room. I would try and stay above freezing, though. If it is a small room it will not take much time at all for it to be really, really hot! Prepare to be amazed!