Taiwan in May
 

I know that May is rainy season and I'd be spending the bulk of my time hiking in the hills and along the coast. Would you advise going in May, or waiting until a more favorable time of the year?

Not sure I would want to be hiking in poor weather. Landslides seem to be a constant threat. I expect that would be the case even more during rainy weather.

But who knows about the weather these days? I was there in November which was supposed to be clear blue skies and it was grey and showery almost the whole time. Until then it had apparently not rained for months which I was also told was quite unusual. Global climate change is real. [Or maybe it was just ordinary variation....] So my point is that you never know what the weather will end up being like. If you can keep plans flexible there is plenty to see and do all over the country.

Definitely do *not* go hiking in the rain.

Unfortunately, it can be rainy any time. By and large, the north and east are much more rainy than the south and west, so with a little luck and flexibility (as noted above), you'll do OK.