to find out what is going on...the siding would
have to come off around window.

prior to the siding install..did the windows
leak?

better use for spray foam would be roofline & under house.
not walls. not in La.

best of luck.

The leaking below the window is usually caused by an exterior sill that does not have a drip nosing so water can run over the sill and travel back to the siding. Sloppy contractors caulk this junction but it fails after a few years.

The only thing that is not clear is why it is only occurring at the side.

Your problem is your search for a quick fix. A quick fix is what created this mess. You need a comprehensive fix that costs what it costs. Get in contact with a contractor with an excellent reputation and go from there.

Might be leaking someplace else. Guess I'd first prove beyond all doubt it was the window(s) leaking by taping plastic (or some such) over the entire thing; that is isolate it from direct rain.

For sure that would stop the rain. :-)

Leaking windows are usually a symptom of improper flashing, as you deduced. Fix those sills right away to prevent further moisture damage to your beautiful, original windows. You can actually DIY the sills if you can use a saw and have free weekends. Sill stock is sold pre-primed at all the big box home improvement stores. Sills are time-consuming to replace, but your original windows were built with provisions for repairing and replacing any part of them. Fix the drips, but remember that your original wood windows aren't meant to be completely air- or water-tight. The wood needs a chance to breathe and exchange water vapor.

You are to be commended for wanting to keep, and to keep up your original windows. I learned how to restore, maintain, and troubleshoot wood windows because I didn't have the money to pay someone else to do so. If DIYing interests you, check out www.historichomeworks.com. I learned from the nice people there by watching the videos and asking questions on the forums. I am not affiliated with this Website or its owner, John Leeke, but he is something of a personal guru of mine.

Good luck with your beautiful old house!

Here is a link that might be useful: Historic HomeWorks

Water showing at he sills may not be coming in from the sills. I agree a quick fix bandaid is not the correct approach and in effect may cause more damage by not allowing the real water intrusion a path to exit (however horrible what you have going on may be, imagine all that water staying inside the walls. Another factor with that much leakage is mold. You need to find out the real water intrusion places asap and fix it immediately.

I am not looking for a quick fix per se, just a temporary fix until we can get the money together. I want to repair the drywall and have a little time before we can call a contract. Not to mention, getting a contractor out who will be willing to take the siding off my very tall house.

The sills upstairs were removed and slanted. Replacing them is actually harder than it seems (or it seemed so from my perspective when I saw them do it). I think adding the sloping piece of wood over the existing sill seems like an interesting idea for lots of reasons. Am i crazy in thinking that way?

The work on the siding was done before we bought the house. I have no idea if the windows leaked before. The sills are new, though I think (the ones upstairs were). I really can't tell what was done or what the person who did the work was thinking (my normal contractor who fixed the upstairs windows feels the same way).

Thanks for everyone's advice so far!

You haven't shown us what the window looks like from outside so all we can do is guess about the leak which is pretty much a waste of time and pixels. Good luck with it.

Sorry, I didn't think about that. See attached and another in another post.

Here is the window from the outside. It's just two windows because I can't get them all in one shot. Is this OK?