Aruba is a desert island with about 22" of rainfall per year. The worst I have heard about the weather in October is that it can be hot and stale if there is a hurricane to the north. It appears the hurricanes in the caribbean can suck the normal winds from the island.

If there is not a hurricane, then be prepared for constant winds from 8 AM to 8 PM. The gusts are strong enough to pick up sand from the beach and pelt you with it. This happened to me enough that it deterred me from staying on the beach too long.

If it rains, it will be a short shower and move on. Go and enjoy.