Unfortunately, its water soluble. When it rains, it washes away.
Not particularly good really. Plus is seriously expensive. Get some good reflective tape instead.
My wife said that I was pretty hard to see at night time. I tossed on two strips of Red C2 reflective tape I got at Harbor Freight and with just that small addition, my visibility at night greatly improved. It seems like such a small addition but it really does a lot.