Christmas is in summer?

Where Nick is going for Christmas is beyond the range of reindeer, disguised as Santa, he has persuaded an Antarctica-bound military flight to drop him off at his home in Christchurch.

Nick: Can I try that? Wow, got him!

Marine: Good shot. I thought you'd be staying in the northern hemisphere. More work up here.

Nick: I'm only a part-timer. I just helped with loading the rigs. Going down for some warm weather.

Marine: Oh, right. I forgot. They celebrate Christmas in summer down there. Don't you think it's weird?

Nick: Nope. I grew up there. All the books I read were from the northern hemisphere, had reversed seasons, got used to it. Like my body, it's a place I've always inhabited, it's always been like that. It's the norm for me.

...