The code does contain broad requirements that materials and methods be suitable for their environment, and use. So, should a manufacturer submit a product for outdoor use to UL, the UL Lable will say so.
Connectors and such are not required to be "waterproof." Part of the reason for this is that the application -even if outdoors- may arguably place the product in a "damp" location, and not a "wet" one. And even "rain proof" materials are not, by any stretch of the imagination, suitable for submersion.
The "hardware" is but part of the equation...the install is also part. The outdoor circuit is to be GFI protected. Many light sets also contain their own fuses.