You should have let it completely dry out before doing anything more with it!
You do not have a protective case and bag to carry your expensive iPad Pro around outdoors?
Anytime I take my iPads anywhere, the iPad case is covered and I put it into a laptop carry starp bag.
You never know when the weather can turn on you.
Downpour of rain does NOT seem good and even less so for an expensive and exposed iPad.
Water and electricity do not mix.
If you tried charging or doing ANYTHUNG with this iPad while there was still some water present somewhere in the device, you could have done some damage.
Time for a trip to your local Apple Store.
I advise you search online to locate and call contact your nearest, “local” Apple Store location to try/attempt to make an appointment to get your iPad Pro diagnosed and options presented.
Bring your charge cables and charging adapters, too! These could have been affected/damaged, as well, after the fact.
OR, failing that,
Contact Apple support via the contact support link located at the upper right hand corner of every Webpage of these Apple support communities
OR by installing and using the Apple Support app found in the iOS App Store.
Tap the iOS App Store link below.
https://apps.apple.com/us/app/apple-support/id1130498044
If no paid, extended, two-year AppleCare+ protection, this could be a very expensive device replacement.
If you have any paid,, extended AppleCare+ warranty] protection left, then a replacement device will be a much less expensive device replacement fee.
Sorry & Good Luck to You!