Doors and Windows - Window Frame leak

I am a first time home owner, and have a condo on the first floor of a 3 family in the city. We got hit with a bad snow storm over the weekend and on the 3rd day of snow my window started leaking at the top of the window frame. I have been here for 3 years, and it is a building from the 1940's. I know I will not have the skills to fix this myself, but I will not able to get anyone out here to look at it until after the holidays at the earliest if it's an emergency-but financially probably not until the spring if i can help it. Looking around at other threads it appears this may be something as serious as a problem with my siding. I was wondering if there was a do it myself temp. fix, like caulking the top of the window frame, until i can get a professional to find the source of the problem and fix it. My biggest concern is causing more damage than quick fixing the problem is worth. Any advice? Thanks in advance.

Welcome to the forums! You didn't indicate whether the leak was air or water, but since you referred to snow, I am assuming water. Any sealing you do, must be done from the outside in order to stop water from infiltrating. After things melt down, take a good look at the exterior frames of the windows and note any gaps in the caulking, lack of flashing over windows, cracked wood, etc. Air infiltration is a different matter. While good caulk/flashing is required on the outside, you must also address the air gap between the window frame and the actual house framing members. Let us know if we can help further.