I want to go outside at this time of the night and water my plants.
Why do you want to go out so late at night?
I've started to do this recently, it fits better into my schedule.
It's fine to do things at unconventional hours. But ensure you're not changing due to some underlying reason.
What do you mean? I'm fine. There's no need for concern.
There's no reason not to water plants late at night. The only thing to be sure of is that you're not making a lot of noise when you do it, since that might wake the neighbors.