Welcome to the forum this first day of August!
20+ years as an electrician and I've heard a lot of anomalies in homes, commercial retail rental spaces, mobile homes, and office buildings. Many of these seemingly strange events occur when it's raining or excessively dry. Although difficult to track down to the exact source, it almost always ends up being a grounding issue. Either the moisture causes an alternate ground path, or the lack of moisture opens the ground path. Earth ground issues in buildings utilizing AC and frame ground issues in vehicles utilizing DC have the same basic concepts for completing circuits.
The rain or water doesn't necessarily have to have contact with or affect the circuits directly (even though in some cases it does), it's the moisture, condensation from temperature change and/or humidity.
I'd say that it's likely the rain or conditions when it rains is possibly shorting out one of your exterior lights and playing havoc on your interior dash lights as well. Figuring out which one it is might take some time, but since this is a recurring problem for you, when you find the offending light/lamp....it should be rather obvious like maybe some rust coloring around lamp bases or white or green corrosion on a terminal. Most of the vehicle's electrical systems are very well isolated and well sealed from any possible moisture. But it does happen. A loose screw on a frame ground can cause a lot of problems. Rain water can travel a long way through certain channels to cause an issue as well. It's like a roof leak in your house. Where the water enters the roof....and where it leaves a stain on the sheetrock ceiling inside can be far apart due to water running down the rafter until it meets an obstacle and falls off causing the drip to the ceiling.
Anyway......best of luck you finding out where the short is. Maybe you can do this with a garden hose on a dry day with your car in the driveway. Water around each light until they go out? May sound silly, but that's probably what I would do myself without a better clue.
