Do butterflies only fly on sunny days or during the daytime?

Answer 1

The majority of butterflies fly during the day, this is mostly due to the fact that the flowers they feed on emmit light that they can see, but only when the sun is out.
Butterflies and moths alike have sensitive scale covered wings thta are easily damaged by rain, so they try to avoid rainy periods of the day.

I hope this answers your question!

Answer 2

Butterflies do fly on sunny days just as the vast majority of flying insects do. Some are nocturnal in habits, mostly Moths from Sphingidae family, and some other families, some fly at dusk.
Most butterflies don't fly on rainy days because they are slow fliers unlike mosquitoes, they are so fast and they can avoid raindrops and butterflies don't..
On an experiment done in Mexican jungles, we found butterflies are smell oriented, more than eye/sight oriented.