What to Check
Start at the bottom seal. On 1980s and 90s steel doors it's usually a single vinyl bead set into an aluminum retainer, and after enough cold seasons that vinyl cracks or flattens instead of flexing against the slab. Run a hand along it on a cold day. If it's stiff rather than pliable, it's done its job and is finished. Next check the side and top stop moulding where it meets the jamb. Original wood jambs from that build era have often shrunk enough to leave a visible gap at the upper corners, right where cold air likes to find its way in. Look at the astragal between panels too, especially on double doors, since that's a common spot for shrinkage-driven gaps on older stock. Last, check the seal around the opener's weather-stripped panel, if the door has one. One honest note: none of this tells you whether the door itself is out of square. If the gaps are uneven top to bottom rather than symmetric, that's a track or hinge problem, not a seal problem, and no amount of new weatherstripping will fix it.
The Problem
A cold-severe winter doesn't need a big gap to cause trouble. An eighth of an inch under the bottom seal is enough to let frost build along the base of the door on the coldest January mornings, and that frost can glue the seal to the slab overnight. Try to open the door before it thaws and you risk tearing the vinyl or straining the opener motor, which is already working harder in the cold to move a heavier, stiffer door. Draughts also push cold air across whatever's stored near the door and into any adjoining living space, which is common in this area's split-entry and attached-garage layouts from the 1980s and 90s. Over a full winter, an old, hardened seal isn't just an inconvenience, it's a steady path for cold air into the house. The fix usually isn't complicated on its own. The complication is that a door old enough to need new seals is often also old enough to need new bottom brackets or a straightened jamb, and doing the seal without addressing those just buys a season, not a solution.
