What happens if you buy tickets for the zoo in advance and they close that day due to weather conditions like rain will the honor the tickets for another time? Or refund?

I would give them a call but they don't really close for rain. But I will tell you as someone who has been going for 17 years, going in the rain is the best time to go. You basically get the whole zoo to yourself and the animals are more active (usually) so I would just bring a poncho and rain boots :)

I have never known them to close for anything other than COVID.

I'm unsure about that question

I think they will give you a grace day and you can go on the next best day but I would call them and ask.