light switch wont turn off the lamp post light out by the road on some rainey days

Presume then Craig single-pole switch and 2 wires. Of course if you have disconnected them from the switch then there could be no current. So maybe you mean no voltage, and if so then do you mean with respect to one another, to neutral, or to the case (if metallic)

(If a third wire in the box, not connecting to the switch but coming in with one of your wires and going out with the other, it might be neutral)

The neutral or "cold" connection to the lamp should always be in place, not interrupted at all anywhere anytime. Sounds instead like there's a short somewhere between the "hot" wire to the lamp and some other "hot" wire, in which case tho you should find a voltage on both wires

If it happens only in wet weather however we might guess there's a leak in the attic causing an unusually conductive path. It's importat at this point to learn what kind of bulb it uses. As "short" of this sort won't commonly light a typical incandescent bulb but an LED or other semiconductor might shine like mad

Being careful as I gather you've had little contact with electricity (pun intended)

What you are describing sounds very dangerous. If you pulled the switch out of the wall the there was still power on the light, it has shorted to a completely different circuit. I suggest when this is happening, you go down your breaker box and open each breaker one at a time until you succeed in turning the light off. Then you will know where the power is coming from. You might be able to find where this short is if you know what is powering it. Without knowing this, you could electrocute yourself if you try to work on it.