"It's snowing outside, but it is warm at home."

Translation: На улице идёт снег, а дома тепло.

[Frenchyfaith]

I understand "a" can work but why would но not be allowed here? Doesn't it mean the same thing too?

[2E3S]

I think но should be allowed here. It means kind of the same thing here, although но adds more contradiction.