Fencing · Hot & humid

How a wood fence ages in Mobile, AL

THE SHORT ANSWER

In Mobile, moisture — not sun — is the main enemy of a wood fence. The city sees about 133 days with rain a year, mostly from February to February, and its Scheffer decay index of 110.2 is high (#2 of 25 cities we cover). Untreated boards gray within the first year, then mildew and soft post bases become the real problem. Model estimate: 10–13 years untreated, 13–17 years sealed on schedule.

Main threat

Moisture & decay

Climate profile

Hot & humid

Expected life (untreated)

10–13 yrs

Fully gray by

Month 11

Best seal window

May – Sep

Sealed on schedule

13–17 yrs

Simulated wood fence in Mobile, AL after 10 years

Year 10Rot at the base — posts may lean, heavy mildew, deep checks

MODEL SIMULATION

Mobile, AL · cedar pickets on wood posts, no stain

Drag through time 0 — 20 years

Color lossSevere

Surface checkingHigh

Mildew / rotHigh

Fails first herePost bases and picket bottoms

Storyboard

20 years in Mobile, untreated

Wood fence in Mobile, install: Fresh boards — **Install**Fresh boards

Wood fence in Mobile, year 1: Fully gray — **Year 1**Fully gray

Wood fence in Mobile, year 3: Mildew in shade — **Year 3**Mildew in shade

Wood fence in Mobile, year 5: Heavy mildew, surface checks — **Year 5**Heavy mildew, surface checks

Wood fence in Mobile, year 10: Rot at the base — posts may lean, heavy mildew, deep checks — **Year 10**Rot at the base — posts may lean, heavy mildew, deep checks

Wood fence in Mobile, year 15: Rot at the base — posts may lean, heavy mildew, deep checks — **Year 15**Rot at the base — posts may lean, heavy mildew, deep checks

Wood fence in Mobile, year 20: Rot at the base — posts may lean, heavy mildew, deep checks — **Year 20**Rot at the base — posts may lean, heavy mildew, deep checks

Mobile’s wear fingerprint

Each bar is scaled to the highest of the 25 cities we cover; the black line marks the median.

Rainy days / yr133.4 · High

Avg humidity79.2% · High

Decay index110.2 · High

UV index (avg)1.5 · High

Freeze–thaw days15.1 · Typical

Days ≥ 90 °F73 · Typical

NOAA station MOBILE DWTN AP (USW00013838, 8.7 km away), 1991–2020 normals · humidity & UV: NASA POWER.

What fails first here

1Mildew & algaeA wet season from February to February and 79% average humidity keep shaded boards damp; dark spots start near walls, planters and gaps.
2Checks, splits and cuppingStrong UV (rank #8 of 25) dries and shrinks the surface faster than the core, opening fine cracks.
3Rot at post basesThe real lifespan limiter in Mobile: decay index 110.2. Posts rot at the soil line first.
4GrayingCosmetic, and fast: our model has the surface fully silver by month 11. Not damage on its own, but it means the protective surface is gone.

Upkeep

Mobile maintenance calendar

Built from local normals: bar width is the share of days with rain; sealant needs 2–3 dry days between 50 and 88 °F.

Jan

Feb

MarInspect ends & fasteners

AprWash off mildew

MayStain / seal

Jun

Jul

Aug

SepStain / seal

Oct

Nov

Dec

Same city, other materials

How the alternatives age in Mobile

Cedar deck

Expected life here: 9–12 yrs · main threat: moisture & decay

See it age in Mobile →

Composite deck

Expected life here: 23–30 yrs · main threat: moisture & decay

See it age in Mobile →

Pin-ready

Save it for when you build.

The 20-year storyboard as a tall pin, linking back to this page.

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Pinterest storyboard: wood fence in Mobile, AL, new to year 20

Wood fences in similar climates

…and in very different ones

Las Vegas, NV

Phoenix, AZ

Denver, CO All 25 cities →

Questions Mobile owners ask

How long does a wood fence last in Mobile?

Our model puts it at 10–13 years untreated and 13–17 years if it is sealed every 2–3 years. The national typical range is 15–20 yrs; Mobile’s moisture & decay profile is why the local number differs.

When is the best time to seal a wood fence in Mobile?

May and September: the months with the fewest rainy days while average temperatures sit between 50 and 88 °F. Most sealants need 2–3 dry days to cure.

How long do fence posts last in Mobile?

Posts are usually the first part of a wood fence to go, because they sit in damp soil. With a decay index of 110.2 here, plan on inspecting post bases from about year 6.

Why does wood turn gray or black in Mobile?

Graying is UV plus weathering of the surface; black spots are usually mildew or algae feeding on that grayed layer in damp weather, not rot. A cleaner and a dry-season seal stop it.

Model simulation, not a guarantee: south-facing, full sun, no shade or ground-contact surprises. How it works.