I'm working on a story where a character gets trapped in a cave but use his knowledge as a weatherman to navigate and escape! Are the any weather-related clues you could use to escape a cave specifically? The more unusual the better! Would love to hear your ideas!
When you say "trapped" I presume you mean he cannot find his way out, as opposed to being trapped by rock fall or something blocking his exit such as flooding?
The only weather-related clues could be when reaching to very near an entrance where the temperature can change. Caves tend to be at a fairly constant temperature (around the average for the location) and it is possible to feel a rise or fall in temperature as an entrance is approached.
Rain or melting snow can affect the level underground water courses but this would not help in navigating to the entrance as the water may have reached the current location via a large waterfall or other impassable obstacle and a change in level would not give any additional clues to help find a way out. The direction of flow would not be useful unless you knew that the water was flowing into or out of the cave anyway.
It is also possible that a change in atmospheric pressure could change the direction of any detectable air currents underground. Possibly if the pressure was known to have changed causing the air in the cave to change direction and either flow into the cave when the pressure rises or out of the cave when it falls, this may help if finding a direction towards an entrance. Again, there may be obstacles in the way as the air can flow through spaces a lot smaller than a person can get through.
As the outside pressure increases or decreases the air inside a cave has to equalize. The most common cause is a pressure change is when the the outside temp changes due to the sun rising or setting. A front will also affect this.
The larger the cave, the more air will go in & out. The air will feel like a wind. This is more noticeable near the entrance as that's where the most volume of air is passing. But can also be felt far inside, especially in narrow passages.
The direction of the wind will depend on if the cave is breathing in or out. The cave breathes in when the pressure outside increases.
The only other weather indication in a cave is the water level may rise when it's raining outside. But this would not be helpful in finding an exit.
Source: I have spent many, many years caving as a hobby.