Thanks everyone!
So I just got back from Rio, and did the ex-GIG on UA biz, lie flat was nice. RIO temps are overshooting it, like 100F 100% humidity. I considered MEX but couldn't find the flight, ended up x-ferring 10,000 MR -> DL and did RT LHR. It's not much better temperature wise than DC but there's no snow on the ground and it's a direct flight. Already caught a show