Have fun.
It might sound weird having one in winter, but we went to the Blue Lagoon in Iceland one night when it was around freezing point. The water was beautifully warm, and we just lay back, looking at the stars.
I imagine this will be quite similar.
You need it to be freezing for a hot tub to be worthwhile, otherwise you don't get the full benefit. First one we did was a cabin in the lakes, -2 and we were loving being in the tub, although getting out was a bit sketchy.
Been out in it tonight already, couple of beers, kids off the playstations, ideal.