Frost Line Depth in Forrest County, MS: Set Locally (Gulfport: 12 in)

No official local value

No official frost line depth is published for Forrest County.

No verified code nearby. The only verified Mississippi code we read, Gulfport’s, uses 12 in.

Source and how we checked

We searched this place’s own code and website and found no published frost line depth.

Climate: 34 nights a year at or below 32 °F (NOAA 1991–2020, Hattiesburg Chain Municipal Airport, 6.5 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

12 inGulfport, the only verified Mississippi code
34nights a year at or below 32 °F
100%of nearby soil rated “none” for frost action (USDA)

Does Forrest County have an official frost line depth?

No adopted frost line depth found for Forrest County in its official documents (checked Oct 2026). No verified code lies near Forrest County; the only Mississippi code we verified, Gulfport’s, uses 12 in. Ask the building department for Forrest County’s own number before you dig.

What frost line depth does Forrest County use for footings under Table R301.2(1)?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Forrest County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 12 in (the deepest verified state value) unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

How deep do footings, decks and water lines need to be in Forrest County?

Drawn with the deepest Mississippi official value (12 in). Confirm Forrest County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Forrest County: dig at least 12 in (30 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 12 in until Forrest County confirms its own
Project	Depth	Rule
House or garage footing	12 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	12 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	18 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	12 in	No code rule; common practice is below the frost line

Work out posts, concrete and footing sizes with the fence post depth calculator or the deck footing calculator.

How cold does it get in Forrest County?

Forrest County never averages a low below freezing. 34 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 38.1 °F.

NOAA 1991–2020 climate normals, Hattiesburg Chain Municipal Airport station, 6.5 mi away, elevation 151 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	38.1	41.7	48.1	53.9	62.3	69.5	72.3	71.8	66.9	55	44	40.5
High	60	64.5	71.5	78	84.6	89.8	91.6	91.8	88	79.6	69.2	62.3

Forrest County has fewer freezing nights than 10 of the 17 other Mississippi places we track. The Mississippi median is 41. Coldest: Olive Branch; mildest: Biloxi.

How likely is the soil in Forrest County to heave?

None 100%

USDA rates the sampled soil around Forrest County as 100% none for frost action (main soils: McLaurin, Ruston, Benndale).

USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.

Forrest County at a glance

Frost line depth: No official local value
Population (2023 est.): 78,208
Mean annual temperature: 66.5 °F
ZIP codes (8): 39401 · 39402 · 39406 · 39425 · 39455 · 39465 · 39475 · 39577