99 Corolla won't start in/ after rain

[Some Guy named Dan]

It starts with no problem regularly, it even starts in 15-degree cold and during a snowstorm, but it won't start while it is raining and after it rains for about 24 hours.

It’s dry under the hood and doesn’t even look moist/ damp on the visible electrical connections.

If I jump it at high RPM for about 10 minutes it starts- sometimes.

I’ve Googled and YouTubed this a few times and not gotten many ideas- and the things I've found don't seem close- but I’m not a mechanic.

Battery and plug wires are ~1yr old.

It’s getting to be really aggravating.

Any help would be greatly appreciated.

Thank you.

[maxwedge]

Moved to proper Toyota forum.