PR has a dry season when the island receives less rain, and there are dry regions that generally get less rain. In fact, there are sometimes forest fires [1].

Regarding construction, I've never seen a smoke alarm inside a residential building in PR. I would hazard a guess that this is allowed for concrete/cinderblock; presumably the roof thing is the same.

[1] - https://www.elnuevodia.com/noticias/seguridad/notas/incendio...