Just got caught in major rain, no power after I turned car off

I don't have a test light, but can get access to one if I don't find any obvious issues. I do know for sure that the battery terminals are clean and tight, me the battery itself is not the issue. I bought it new on Friday, and neither a fully charged jump box or jumper cables connected to my running Jeep would even get the dome light on. The rain let up a little bit ago, so I went out and tried to trace the positive battery cable, but it's too dark. Hopefully I can check it over again tomorrow before work with some sunlight and a clear head.