As is discussed at length on these forums, the Airstream isn't as well-insulated from exterior conditions as a modern house, and the aluminum structure is good at conducting heat. This means you'll be more aware of exterior weather conditions.
That said, my '75 Argosy did OK in the shade at 102F, the AC was able to bring the temperature down to the point at which the compressor could cycle on and off (it DID take a while to get there, of course.) I've no cold-weather experiences to share, but that's been done as well. People recommend some sort of skirting to keep wind from blowing underneath the trailer, and the built-in furnace needs to run to heat the tanks and water lines in the belly. People generally describe our Airstreams as "3-season" trailers. I wouldn't want to live in one in a Minnesota winter unless it was parked in a heated barn.
Il Carriaggio — 1975 Argosy 24 | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill