No stopping power when wet - brake calipers or pads?

[predki]

I had the same pads mounted on Campagnolo calipers, that came with one of my bikes. Hard as a piece of stone, scratching rims with unpleasant sound, completely useless... Calipers should be alright, so just change the pads. From my experience you can adjust almost all calipers to give you enough stopping power, even with steel rims on wet with good pads. The weak point of stopping is always between tyre and the ground. I use Koolstop pads for my Mafacs brakes and some Campagnolo (although original ones for Campagnolo are good). Salmon are intended to stop better in wet conditions

and as Ian said:

If you are riding in wet weather always remember to brake gently once in a while to clear the water off the rims.

 

[Ian Raleigh]

Do I need to replace the brake levers too?

Not really unless they are broken.