Truck radio comes on by itself

I have a 99 Ford Ranger, 6cyl, automatic. I don’t drive it much, only on weekends. The last 2 weeks, when there has been a thunderstorm at night, the next day, the radio in the truck is ON. The doors stay locked and the key is not in the truck so no person has been getting in and turning on the radio and leaving it for hours. What do I need to do so this doesn’t happen again? Anyone else have this problem?

I would be tempted to put a switch on the power lead to the radio. You could mount the switch under the dash. You will lose your pushbutton settings, but if you only use the truck occasionally, this may ot be a problem.

Try this test ;
With no key in the ignition lock, wiggle the cylinder yourself. Back toward the accessory mode, forward to the on mode. Can you make the radio come on ?

If the radio is on next time try the “no key wiggle test” to see if you successfuly turn it off.

Theory has it that the thunderstorm may provide enough sound concussion to jiggle a worn out ignition cylinder or ignition switch just enough to contact the adjacent terminals in the switch.

Ghosts are friendly if you’re friendly to them.
Ask him nicely to go play at the neighbors.

Is it always same station,same volume? When power is disconnected then reconnected the radio usually defaults to lowest frequency (and likely not a frequency transmitted on). Or is the radio on the same station it was when you turned the radio off. Are you turning radio off with its power knob or leaving power knob untouched and just shutting key off? I am exploring the ghost possibility.