That doesn't sound dumb at all. In fact, rain is one of my favorite diagnostic clues.
If your transmission only acts up when it's raining, I probably wouldn't start by blaming the transmission.
I'd start by looking for water getting somewhere it doesn't belong.
I've found rain-related problems caused by:
Moisture getting into electrical connectors.
Wiring insulation rubbed through just enough for water to create a short.
Poor grounds that only act up when they're wet.
Water intrusion into a fuse box or control module.
Even wheel speed sensors or ABS wiring getting contaminated with moisture.
Remember, your transmission depends on information from a lot of different systems. If a wheel speed sensor starts sending bad information because of water, the transmission can shift differently even though there's nothing wrong inside the transmission itself.
One thing I've learned over the years is this:
Weather doesn't create problems—it exposes weaknesses that were already there.
That's why I always ask customers to tell me exactly when it happens. Does it start as soon as it begins raining? Only after driving through puddles? Does it happen after the truck sits outside overnight? Those details can cut hours off a diagnosis.
So no, I wouldn't dismiss what you're experiencing. I'd consider the rain a valuable clue. Sometimes Mother Nature does the hard part for us by recreating the condition that makes the problem show itself.
That's where I'd start looking.