weird leak top floor

hi .. 5 years ago I had water leaking from the ac/heat vent on the top floor .. it was about a bucket and I was lucky to notice it right away and contain it ... I found no traces of water leak in the attic ... this past summer I had few shingles blown off the roof by the wind ... I had a contractor come in .. he did the fix and maintined the roof and then assured me I will be good for the next few years ... last week I discovered a water leak that left a bubble of water in my lower flower drywall ceiling .. about half a bucket .. I was lucky to be at home and it was not too late ... this time the water came from the smoke detector ... no traces of leak in the attic ... both incidents happened when the temperature was below freezing ... both incidents the water stopped on its own ... both leaks stopped within half an hour ... first incident was snow day.. 2nd incident freezing rain and then pouring rain ... both were in the same room ...
anyone experienced a similar situation? any clue where the water might be coming from? ac? roof?
where should I be looking?

thank you!

 

I'd start by checking the seals on the vents on the roof.
Since it's that cold there it could also be ice dams

 

Where are you located?

Ice dams are a possibility depending on your location. It also could be wind blown rain getting underneath some flashing or a nail pop on the roof. You'll just have to do some investigating and follow the leak back to it's source.

If you can buy or borrow a thermal camera they can be very helpful finding the source of a leak. When looking at the ceiling in your house you'll see the smoke detector or wherever the water is collecting as a cold blob. Then you can look at the ceiling around it and the walls for cold streaks indicating where the water trickled down.

 

thank you, I live in the DC area around Dulles Airport.
I ll see if Lowe's or the Home Depot rent thermal cameras on an icy day

thanks again!

 

There are inexpensive thermal cameras available now including ones that plug into a smartphone. Renting would be cheaper and get you a higher resolution camera which makes identifying things easier.

Any chance you can get up on your roof? If not try to pay attention to the weather around when you have the leakage. Ice dams require one kind of weather while wind blown rain another and each will tend to leak in different locations so narrowing it down will help find the culprit.