outdoor speakers usually are constructed to resist humidity and indirect rain/moisture. The speaker cones are a poly material and the speaker surrounds are usually rubber instead of foam. The cases are weather-sealed.
You can find very good pricing on Polk Atrium outdoor speakers, in several sizes, from the eBay store "Polk Audio Direct" and/or eBay seller "polkdirect"
CL2 wiring should work fine, leave several feet of extra wire in the ceiling so you can clip off a few inches of wire every couple of years to expose new clean copper for the connection.