We're doing the same trip (reversed) over Christmas and New Years. We have two sets of friends who have done it in February and March respectively. My guess is that it will be a bit chilly whenever you go because South America extends almost to Antarctica. I checked in my Fodor's S.A. book. Here are some of the average temperatures in November:
Buenos Aires 76 degrees f.
Punta de Este 79 degrees f.
Santiago.............78 degrees f.
Punta Arenas.... 54 degrees f.
As you can see, the southern locations will be chilly but the more northern cities will be mild. Here are the same stats for March.
Buenos Aires.....79 degrees f.
Punta de Este....78 degrees f.
Santiago.............. 80 degrees f.
Punta Arenas..... 54 degrees f.
My take on it is that there is little difference. Here are the Dec. Temps:
Buenos Aires.......82 degrees f.
Punta de Este...... 79 degrees f.
Santiago............... 83 degrees f.
Punta Arenas ...... 57 degrees f.
I hope this helps you choose your date of travel. Please let me know how your trip goes
regardless. Who knows, we might even end up on the same sailing. I'll be the one with a grin on his face. Bon Voyage!
My husband and I went from Valpariso to Rio last March on the Mercury. It was a great trip. The weather was extremely hot in Santiago/Valpariso and Rio. The trip around the horn was cold and windy. So, you'll need to pack accordingly. I don't think there are any self-service laundries on any of the Celebrity ships. We try to bring as little as possible on our cruises, and this was a tough one to pack for. I didn't bring nearly enough work out clothes.