Change plans without losing the day
If it rains, you can reshape the day around museums, cultural centers, AquaRio, cafés, and food. I would choose one area and two compatible activities instead of spending the day crossing Rio in the rain.
With a baby or stroller, I would first check whether the venue has easy access, a restroom, and space for a break; I would not assume every building or route offers the same conditions. If there is an official alert, heavy rain, or flooded streets, I would postpone the visit and follow local guidance.
Before you go
Check practical details for the day of your visit. Hours, access conditions, and available services can change.