When sourcing outdoor speakers, the IP (Ingress Protection) Rating is the most vital metric. You should prioritize products with at least IP55 for general rain resistance or IP66/67 for high-pressure water jets and temporary immersion. Additionally, ensure the housing is made of UV-resistant ABS or ASA plastic to prevent cracking and discoloration under prolonged sunlight, and verify that the speaker cones are made of waterproof materials like polypropylene or carbon fiber rather than treated paper.