I have couple of older Cateye AA LED lights that I still use as side blinkies in the rain or fog. They held up well in the rain.

One thought to keep in mind is that the same light that worked well in ideal condition will be much less in performance in a downpour. My setup is overkill in a clear day and I run them on Low or MED but when it is downpouring, I have to run them on Hi to get the same effect.