Recaulk the corner flashing if any areas have hardened caulk.
Fix a leaking roof in winter.
The secret to caulking in winter time is to heat the sealant in the tube.
Now is a time when you can start planning if you know where to start.
Shine a flashlight along the underside of the roof and look for a hole in the roof as well as areas that are wet or have been.
Dig out any cracked or dry caulking that isn t properly sealing adjoining surfaces and replace with silicone caulk.
The shingles can be warmed up with a propane torch.
Start low soaking the area just above where the leak appears in the house.
Identify the potential source of the leak.
Shingles that aren t stuck to one another are very susceptible to damage in winter winds.
Locate the source of the leak by examining the underside of the roof from within your attic or crawl space.
The roof shingles should be softened and flattened as the shingles tend to curl up in winter.
Make use of the flame carefully on the curled shingle edges.
Isolate areas when you run the hose.
In the winter a dab of roofing cement or tar should be added to each shingle to bond them together until the tar strip is activated in warmer weather.
Locate the leaking source and search for the damaged or missing shingles and make a list of the areas to be repaired.
Perhaps placing tube on furnace duct so air heats pre cut tube inside of home then climb up ladder and seal area keeping the sealant warm and easily caulk able.
Replace any missing or rotted siding above the step flashing on dormers.
The tar strip needs to be about 60f to activate.
For example soak the downhill side of a chimney first then each side then the top on both sides.
Sealing the shingle to the object can be accomlished with a roofing sealant available at menards lowes etc.
Your best solution may be to just tarp off the problem area until the spring but be sure not to block off any venting pipes that vent out dangerous gasses.