Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 39521 — Bay Saint Louis, MS

ZIP code 39521 (Bay Saint Louis, Hancock County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is March 6 and the first fall frost November 19.

Where ZIP 39521 is

tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone9a20 to 25 °F
Coldest night−6.7 to −3.9 °C
Last frostMar 6
First frostNov 19
2012 zone9a

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Bay Saint Louis, MS…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Bay Saint Louis, MS

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 6median — 50% chance of a later frost
Safe for tender plantsMarch 27only 10% chance of frost after
First fall frostNovember 19median — 10% chance by Nov 3
Growing season262 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 16 and returns around December 4.

From the NOAA station Bay St Louis Nasa, MS — 6 miles away, elevation 30 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 39521

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 23 – Feb 6
SpinachSow outdoors · Jan 23 – Feb 13
Broccoli, cabbageStart indoors · Dec 26 – Jan 9
Broccoli, cabbageTransplant · Feb 13 – Feb 27
Onion setsPlant outdoors · Feb 6 – Feb 20
PotatoesPlant outdoors · Feb 13 – Feb 27
LettuceSow outdoors · Feb 6 – Feb 20
Carrots, beetsSow outdoors · Feb 13 – Feb 27
TomatoesStart indoors · Jan 9 – Jan 23
TomatoesTransplant · Mar 13 – Mar 27
Peppers, eggplantStart indoors · Dec 26 – Jan 9
Peppers, eggplantTransplant · Mar 20 – Apr 3
BeansSow outdoors · Mar 13 – Mar 27
Sweet cornSow outdoors · Mar 13 – Mar 27
Cucumbers, squashSow outdoors · Mar 13 – Mar 27
Fall lettuce, spinachSow outdoors · Sep 24 – Oct 8
GarlicPlant cloves · Nov 5 – Dec 10
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 6) and first fall frost (Nov 19) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 39521 came on Jan 11 — 15 days earlier than the 1991–2020 average (Jan 26).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 9a in Mississippi

541 plants native to the lower 48 states, recorded in Mississippi, and rated by the USDA to survive 20 °F or colder — the bottom of zone 9a. Each links to its USDA PLANTS profile.

Trees 80

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °FAtlantic white cedar50 ft · blooms spring · medium shade tolerance · to −36 °F

Shrubs 119

aloe yucca15 ft · blooms early summer · medium shade tolerance · to −1 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican beautyberry6 ft · blooms early summer · medium shade tolerance · to −8 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °F

Wildflowers & perennials 167

American bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °FAmerican spongeplant0.5 ft · blooms mid spring · high shade tolerance · to −24 °FAmerican water horehound1.8 ft · blooms early summer · low shade tolerance · to −38 °F

Grasses 153

American cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °Fbig bluestem6 ft · blooms summer · high shade tolerance · to −46 °Fbig cordgrass8 ft · blooms spring · high shade tolerance · to −3 °Fbighead rush3 ft · blooms early summer · low shade tolerance · to 12 °F

Vines 13

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fcupseed30 ft · blooms late spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Bay Saint Louis, MS.

Soil in Bay Saint Louis, MS

The soil mapped at the center of ZIP 39521 is Saucier — fine sandy loam, moderately well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Saucier fine sandy loam, 5 to 8 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 39521; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Bay Saint Louis, MS

Summer high89 °Faverage high, July
Winter low40 °Faverage low, January
Hot days80days a year at 90 °F or more
Freezing nights31nights a year at 32 °F or less
Growing degree days6,027base 50 °F — the season’s usable heat
Longest day14 h 07 mindaylight on June 21
Shortest day10 h 11 mindaylight on December 21
Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb
Precipitation65.9 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°32 °FJanuary: average high 60 °F, low 40 °F 60°40° JanFebruary: average high 64 °F, low 43 °F 64°43° FebMarch: average high 69 °F, low 48 °F 69°48° MarApril: average high 75 °F, low 54 °F 75°54° AprMay: average high 82 °F, low 62 °F 82°62° MayJune: average high 87 °F, low 69 °F 87°69° JunJuly: average high 89 °F, low 71 °F 89°71° JulAugust: average high 89 °F, low 71 °F 89°71° AugSeptember: average high 85 °F, low 67 °F 85°67° SepOctober: average high 78 °F, low 56 °F 78°56° OctNovember: average high 69 °F, low 45 °F 69°45° NovDecember: average high 61 °F, low 41 °F 61°41° Dec

Precipitation by month inches

0″2″4″6″8″January: 4.99 in precipitation 5.0 JanFebruary: 4.20 in precipitation 4.2 FebMarch: 4.84 in precipitation 4.8 MarApril: 6.12 in precipitation 6.1 AprMay: 4.57 in precipitation 4.6 MayJune: 7.01 in precipitation 7.0 JunJuly: 6.96 in precipitation 7.0 JulAugust: 6.83 in precipitation 6.8 AugSeptember: 6.04 in precipitation 6.0 SepOctober: 3.78 in precipitation 3.8 OctNovember: 4.01 in precipitation 4.0 NovDecember: 6.51 in precipitation 6.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Bay St Louis Nasa, MS (6 mi away); precipitation: Stennis-Diamondhead, MS (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9a.

395229a
Stennis Space Center, MS · <1 mi
395569a
Kiln, MS · 5 mi
395299a
Stennis Space Center, MS · 6 mi
395259a
Diamondhead, MS · 8 mi
395209a
Bay Saint Louis, MS · 9 mi
395769a
Waveland, MS · 10 mi
394669a
Picayune, MS · 12 mi
395589a
Lakeshore, MS · 12 mi

All 2 ZIP codes in Bay Saint Louis → · Mississippi planting zones →

Questions about 39521

What planting zone is ZIP code 39521?

ZIP code 39521 (Bay Saint Louis, MS) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in Bay Saint Louis, MS?

The median last spring frost (32 °F) near 39521 is March 6; after March 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Bay St Louis Nasa station.

When is the first frost in Bay Saint Louis, MS?

The median first fall frost near 39521 is November 19, giving a median frost-free growing season of 262 days.

When should I plant tomatoes in 39521?

Start tomato seeds indoors around Jan 9 – Jan 23 and set transplants outside around Mar 13 – Mar 27, one to three weeks after the median last frost.

How much rain and snow does 39521 get?

About 65.9 inches of precipitation a year (NOAA 1991–2020 normals, Stennis-Diamondhead station).

How hot do summers get in Bay Saint Louis, MS?

The average high peaks at 89 °F in July, with about 80 days a year at 90 °F or more.

What kind of soil does 39521 have?

The USDA soil survey maps Saucier at the center of ZIP 39521: fine sandy loam, moderately well drained, pH about 5.0 (strongly acidic).

Did spring come early in Bay Saint Louis, MS in 2026?

Spring leaf-out near 39521 came on Jan 11 in 2026, 15 days earlier than the 1991–2020 average (Jan 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Bay Saint Louis, MS?

Short-day onions: the longest day near 39521 is 14 h 07 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.