How do you think the people of Noah's day felt when it started to rain?

If there had been no rainfall (as we know it) up till then, with mists watering the ground like it says about the garden of Eden, they would have been astonished. Then when the springs of water from under the ground burst up in monumental fountains they would have been terrified. Considering that the first rainbow seemed to appear after the flood, that also lends itself to the view that no torrents of rain from the clouds had happened before the flood.

They probably realised they had missed the boat (literally).

They felt like fools for not believing Noah, and they also felt very afraid because they had never before seen water fall from the sky...

It's just a shower.

They probably paniced wishing they has listened to Noah.

They got mad at the weatherman for getting the forecast wrong. Same as today.

the animals loved it

They probably thought it would stop when it didnt they panicked. Im sure when some of them started to drown they clawed there way to the ark and begged noah to be let in but noah couldnt. Imagine hearing that people drowing clawing away at the ouside of the ark begging to be saved. Not all of them were evil people.

Wet

They thought it was just a passing shower.