Originally Posted by
rekmeyata
All front and rear bicycle lights are waterproof, now that doesn't mean you can use it scuba diving, but it does mean they will hold to hard wind driven rain with no problems.
The rear lights again all are water proof. The brightest ones on the market are the Cygolite HotShot with a 2 watt LED cheap at $31; the Cateye Rapid 3 for around $30; and the Blackburn Mars 4 for around $21. The Mars 4 is the 2nd brightest of the 3 but it has the best side illumination of the 3, the HotShot is the brightest of the 3 but is the 3rd best for side illumination.
I've had good luck with waterproof headlights -- Cateye, Cygolite, and of course BuMM, all work well through downpours.
Less luck with tail lights. I've tossed a Planet Bike tail light because of moisture intrusion; the switch corroded. NR Cherry Bomb failed too; I don't know what happened but it doesn't work after the first good downpour. Cateye taillights have survived those showers while adjacent to the failed PB lights, and more; but I've also lost a Cateye and BuMM that fell apart crossing railroad tracks and shattered.
I'd split my money and buy two Cateye tail lights -- you've got a better chance of catching the batteries draining before they quit, they're relatively cheap, and they're good enough.