I had new vinyl siding replaced and all my windows look like this. Do I need to caulk this seam where the vinyl meets the white portion of the window (I know not to caulk the weep hole)? Seems odd to allow water to penetrate that boarding behind the siding. The joint is easy to pull away from the window, which the first picture shows.
I'm going to reject the premise of your question outright. Windows should be flashed properly and the siding should have a drain plane installed behind it. This isn't a job for caulk.
Some thoughts that may be helpful:
- In modern construction, sill flashing and house wrap provide the actual weatherproofing around and below windows. Your home appears to have neither.
- Vinyl siding provides visual appeal and protection against physical damage. It does not offer much in the way of weatherproofing. Air and wind-driven rain move freely around it.
- That gap is too large for caulk, and the vinyl channel is too flexible as a base for caulk. It would look terrible, and it would likely fail.
- Vinyl siding is meant to move as it expands and contracts due to temperature, and rarely should it be caulked.
I'm afraid I don't have a great solution for you here. Your siding replacement was done very poorly, and there are no shortcuts to a resolution. Your siding contractor failed miserably, in my opinion, by not providing a path to a viable outcome.
This gap should be filled with foam backer rod that looks like this:
It comes in a variety of sizes up to 3/4" and is designed to be pushed into gaps to fill most of the space. You may need a couple of different sizes, depending on the size of your gaps. You may also need to push more than one piece into the gap along any given side to ensure that most of the space is filled up and the top of the rod is near (but not flush with or above) your desired finished surface. You then caulk over the top of the rod, filling the surface with a nice looking bead of caulk.
When you're done, you step back and say "I meant for that to happen!"*.
Of course, the better option would have been to have the siding company do a better job of trimming out around the windows in the first place, but that's probably water under the bridge by now.
*Warning: that's a link to a really bad movie, like 0.05 stars out of 100, you really don't need to click it. Stuff like that will stick in your head for a lifetime if you're not careful...