GFCI doesn’t protect against arcs, so AFCI would be necessary to protect against arcing causing fires.

The danger with outdoor outlets is short circuiting (like when water drips onto a live wire), so GFCI is almost always required of outdoor outlets. Generally, outdoor outlets also require covers that keep the receptacle dry, at least when not in use (and more modern code generally requires it have an “in-use” cover that can stay on even when something is plugged in).

But having GFCI isn’t the same as AFCI, so arc fires can still theoretically happen.