Normal
We did a 5 day out of Galveston at the end of last January. Temps were noticeably warmer as we got halfway through the Gulf. In Progresso/Merida, the daytime temp was in the low 80's. We had a Mayan ruins tour and walked enough to work up a little sweat, but not uncomfortable in shorts. Cozumel was just as warm. On-deck activity was mostly during the southernmost portion of the trip, and pool temps were chilly!!!