Leaking window

[EddieL]

I just found some very minor water damage to a box in a storage area that is below a window in the slide. I don't know if the window is leaking or the water came from something else but when I inspected the window on the outside I found that there is a gap between the fiberglass body and the frame of the window. There is a seal that if working correctly should seal the window but it seems that it could be an issue when water collects in there and freezes. All the windows look like this so I am going to calk around the windows and watch the area to see if it gets damp again.

My question is what would be the best type of calking for this? And is there anything I should avoid?

Additional info:
The area and box are dry now but it has been stored under ground for the winter although it has rained since I brought it home.

Thanks,
Ed

[SeaDog]

What do you mean "stored under ground" with windows it is very important to ensure the weep holes are clear so that there is not water build up. Stay away form silicone.

[EddieL]

In a limestone mine, so there was no rain, snow or ice on the camper. The weep holes are all open, I just want to seal around the window frame but want to make sure it is something that will stick to both materials and will last.