Do you live in the hinterlands away from the Sound? 5-10F is pretty darn cold for here but I realize that some parts of western WA could see those temps. Where I live it rarely falls below about 20F.

Most hybrid hardy Fuchsias would be at risk in a pot. The reason is their roots would freeze, and possibly freeze-dry, during a prolonged cold spell.

It would also depend on the size of the pot, and where it was situated. In a sheltered alcove, sitting on the ground, they'd probably be oK.

I think the local Fuchsia society rates them H1, H2, and H3. H1 means "forget it", H2 means its hardy in the milder areas of WW, or with a heavy mulch, and H3 means generally hardy once established. The hardier of the H3s might make it in a pot.

Fuchsia magellanica is pretty darn coldhardy; it would probably make it. So too probably would F. campos-portoi and a few others like F. regia.

If the pot is not too delicate, you can very easily protect potted Fuchsias: just bury the whole pot out in the garden level with the surface of the ground, and mulch the top.