As I mentioned before, those examples that I gave you, and that you're using for your question here, are from the Japanese grammar book Particles Plus by Atsuko Kawashima (Harcourt, Tokyo 1992).
About your first alternative translation:
The dog is barking, but someone is outside, right?
In the original Japanese sentence 犬がほえている is merely a justification for asking the question that follows, as in "Do you think there may be someone outside? - Why do you ask? - Because the dog is barking" reversed. In your translation though, you introduce a slightly different relationship between A and B, and the "is" to me underlines sort of an inversion of the relationship between the clauses; The main topic should remain "is there someone outside", but becomes more of "why is the dog barking", like "The dog is barking, but I think there's a reason (that being someone prowling outside)".
Your second alternative translation:
I had heard that it was cold in this region, but it really does get very cold everyday.
I think this one is acceptable, even using "but". If you do choose to use "but" though, it's in the context that the speaker did not really believe it when he or she was told about the cold, or at least that he or she didn't think it would be that cold, so there's surprise. It's hard to argue that this is not the case, but it doesn't have to be so (I'd hazard, it's most likely not); If not, "but" is not the best translation.
I constructed a few more sentences, just off the top of my head, to try and add some more variety:
ね、ミキちゃん、喉{のど}乾{かわ}いたけど、水{みず}ちょうだい。 Hey, Miki, I'm thirsty - give me some of that water.
この説明書{せつめいしょ}って結構{けっこう}曖昧{あいまい}だけど、よくわからないよね。 This manual is quite ambiguous, it's really hard to be sure, don't you think?
健一{けんいち}君{くん}病気{びょうき}だと聞{き}いたけども、車{くるま}を借{か}りてもいいですか。 I heard Kenichi is ill, so would it be alright if I borrowed the car?
In all of the above examples, translating けれども with "but", "although" or something similar (implying contrast) would though grammatically correct make little sense, or would drastically change the meaning from the original. The second sentence is a good example, as statement A and B actually convey the same sentiment (that the manual is hard to understand), despite being connected through けれども.
In the next example, けれども helps introduce a topic:
お父{とう}さんがぼやいていたけど、最近{さいきん}ガス代{だい}はたかくなってきたって。 My father was complaining that recently gasoline has become more expensive.
In colloquial speech, adding a さ to けど (giving けどさ) may in some contexts even more clearly imply that statement A preceding けど just contains some most likely non-vital background information (like how @Yang Muye explained it in his comment on my other reply), or is just a "set-up" for B:
ビール買{か}ってきたけどさ、飲{の}まない？ I bought some beer, you want some?
In this example, the fact that the speaker bought the beer (did not steal it), and in all likelihood did so not very long ago (rather than store beer in vast quantities just in case) is not so important. The question of whether to drink it or not is really what matters the most.
