A few high-end models are, but most are described as “water-resistant.” The challenge is that there’s no common standard for this, so you’re taking the manufacturer’s word for it. Water ingress won’t damage the solar panel itself, but it obviously isn’t good for your phone, tablet, or laptop. An integrated rain hood offers extra protection, but if you’re expecting to be out in heavy rain, we suggest a backpack cover like the one recommended above, or you could use separate waterproof bags for each item you want to protect.