Roof leaks are sneaky because water travels along framing before it drips, so the stain on your ceiling is often nowhere near the actual hole. Finding the source takes a bit of detective work.
Start in the attic
On a rainy day or with a helper running a hose on the roof, go into the attic with a flashlight and follow the water uphill from the wet spot to where it enters. Look for water stains, wet sheathing, and daylight.
Check the usual suspects
Most leaks happen at penetrations and transitions, not in the open field of shingles — around vents, chimneys, skylights, and in valleys where flashing fails. Inspect these areas closely for cracked sealant, lifted flashing, or missing shingles.
Temporary vs permanent fix
A tarp or roofing sealant can stop a leak temporarily, but trace and repair the real source before water rots the structure. Persistent or hard-to-find leaks are worth a roofer's inspection.