When is the best time to travel to taiwan?

Considering temperture-wise and rainfall situations, Nov. to the next Mar. is the best timing to trip there. Between Apr. and May, I recommend you travel in Apr. when it will rain much less and outdoor activities are more accessible than that in May.

Hey! Happy to hear that you are thinking of traveling to Taipei. The city is full of life and is known for its amazing Nightlife. Two months is really great time to visit here. After second week of june, there may be chances of typhoon. At that time, You just have to lock in your room and you will not be able to enjoy it. So just check 2-3 days before the weather of Taipei and plan everything accordingly.
Hope to see you soon.