Wet weather starting

my 1998 jetta will not start when it rains.

It is a stick shift. What’s up?

I suspect it’s gas right?

You likely have wet wires or coils, etc.

The next time it’s been dry for a couple of days and the engine runs good, pop the hood and lightly spray water (use a spray bottle) on the plug wires (preferably one at a time) and coil.

Getting everything wet at once won’t allow you to pinpoint the problem area.

Another trouble shoot you can do is remove the battery cables at each end and clean the contacts/connectors and reinstall them wrench tight.

When that is done, apply a light coating of dielectric grease over the connections to repel moisture.

I would strongly suspect the spark plug wires, particularly if they are the originals. The distributor cap (if it has a distributor) is also a possibility.
What you described is a classic symptom of cracked insulation on the spark plug wires and/or a cracked distributor cap.

I agree. Tune-up with new plugs, wires, and cap and rotor if it has it. Classic worn ignition symptoms.