Stalls when put in gear

Welcome to 2CarPros.

Interesting when it doesn't do it. Rain usually causes electrical problems. However, since that is the case, I think I want you to start with checking for engine vacuum leaks. Here is a link that shows how it is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

It could also be due to a dirty throttle body. You may want to try cleaning the throttle body. Here is a link that shows how it's done:

https://www.2carpros.com/articles/throttle-actuator-service

Also, take a look through the next link. It discusses common causes of an engine stalling at idle.

https://www.2carpros.com/articles/stall-at-idle

Let me know if any of this helps or if you have other questions.

Take care,
Joe