It looks like you are right. I thought Aruba was all semi-arid, but I just found this:
Aruba is the Caribbean’s most revisited travel destination and there’s no surprise why! It was certainly the
most diverse Caribbean island we have been to.
One half of the island is a tropical paradise and while the other half is an arid desert! Also its way out of the hurricane belt so you are guaranteed good weather for the most part of the year. Planning a trip this spring/summer? Check out my things to do in my travel guide to this “one happy island”
HERE.