Checking It Yourself
Start at the bottom of the door. Manhattan Beach housing runs from 1947 through 2012, with the median build year sitting at 1963, so a lot of garages here still have the astragal seal that came with the door decades ago. Close the door and look for daylight along the bottom edge and both sides. If you can see a line of light, or feel air moving across your ankles when you stand near the door, the seal has hardened past the point of doing its job.
Check the corners too, not just the middle. Rubber that's flattened or cracked in the center but looks fine at the corners is normal wear; rubber that's brittle and flaking everywhere usually means it's original and past its service life. Run a hand along the vertical seals on the jambs while the door is shut - if you can slide a finger under them anywhere, air and dust are getting through there as well.
One honest limitation: a seal replacement fixes draughts and dust, but it won't quiet a noisy track or fix a door that's off its rollers. If the door still rattles or drags after a new seal, that's a separate repair, not a seal problem.
The Seasonal Bit
This area sits in a mild temperate climate band, so you're not dealing with freeze-thaw cracking or the kind of seal failure that comes from ice forming under a door. That's the good news. The bit people miss is that mild, sunny, steady conditions still break down rubber and vinyl over time - it's UV exposure and years of daily temperature swing between morning and afternoon that dries seals out, not a hard winter.
Because there's no harsh season forcing a yearly check, seals here tend to get ignored for far longer than they would somewhere with a real winter. A homeowner in a colder climate notices a draught the first cold snap. Here, the seal can sit cracked and doing nothing for a year or two before anyone notices, usually when dust starts collecting inside the garage or a pet keeps trying to squeeze under the door.
How Local Conditions Play In
Being close to El Segundo, Playa del Rey, and the rest of the coastal cluster in this service area means the mild temperate conditions carry a fair bit of consistent moisture in the air, day in and day out, rather than the big seasonal extremes you'd get further inland toward places like West Carson or Artesia. That steady moisture doesn't crack seals the way a hard freeze would, but it does mean rubber and vinyl stay damp longer after fog or morning marine layer, which speeds up the breakdown compared to a drier inland climate.
Across the roughly 39,906 owner-occupied houses in this service area, the seal issue shows up most in homes built before insulated doors were common, which given the median build year of 1963 is a large share of the stock. If your garage sits on the older end of that range and you haven't replaced the bottom seal since the door went in, it's worth the look before winter humidity settles in for the season.
