Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 37148 — Portland, TN

ZIP code 37148 (Portland, Sumner County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 5 and the first fall frost November 1.

Where ZIP 37148 is

Outlined: the ZIP code area · 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.

Zone7b5 to 10 °F

Coldest night−15 to −12.2 °C

Last frostApr 5

First frostNov 1

2012 zone7a

Was 7a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Portland, TN…

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 Portland, TN

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 5median — 50% chance of a later frost

Safe for tender plantsApril 19only 10% chance of frost after

First fall frostNovember 1median — 10% chance by Oct 21

Growing season210 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 26 and returns around November 11.

From the NOAA station Portland Sewage Plt, TN — 2 miles away, elevation 794 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 37148

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 22 – Mar 8

SpinachSow outdoors · Feb 22 – Mar 15

Broccoli, cabbageStart indoors · Jan 25 – Feb 8

Broccoli, cabbageTransplant · Mar 15 – Mar 29

Onion setsPlant outdoors · Mar 8 – Mar 22

PotatoesPlant outdoors · Mar 15 – Mar 29

LettuceSow outdoors · Mar 8 – Mar 22

Carrots, beetsSow outdoors · Mar 15 – Mar 29

TomatoesStart indoors · Feb 8 – Feb 22

TomatoesTransplant · Apr 12 – Apr 26

Peppers, eggplantStart indoors · Jan 25 – Feb 8

Peppers, eggplantTransplant · Apr 19 – May 3

BeansSow outdoors · Apr 12 – Apr 26

Sweet cornSow outdoors · Apr 12 – Apr 26

Cucumbers, squashSow outdoors · Apr 12 – Apr 26

Fall lettuce, spinachSow outdoors · Sep 6 – Sep 20

GarlicPlant cloves · Oct 18 – Nov 22

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 5) and first fall frost (Nov 1) 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 37148 came on Feb 25 — 4 days earlier than the 1991–2020 average (Mar 1).

average
Mar 12026
Feb 25

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 7b in Tennessee

566 plants native to the lower 48 states, recorded in Tennessee, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. Each links to its USDA PLANTS profile.

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 Portland, TN.

Soil in Portland, TN

The soil mapped at the center of ZIP 37148 is Bewleyville — silty clay loam, well drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

pH5.5moderately acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupBwater soaks in moderately

Farmland classprime farmlandUSDA classification

Map unit: Bewleyville silty clay loam, 2 to 5 percent slopes, eroded.

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 37148; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Portland, TN

Summer high89 °Faverage high, July

Winter low27 °Faverage low, January

Hot days38days a year at 90 °F or more

Freezing nights80nights a year at 32 °F or less

Growing degree days4,529base 50 °F — the season’s usable heat

Longest day14 h 40 mindaylight on June 21

Shortest day9 h 39 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation54.3 inper year, rain and melted snow

Snowfall2 inper year; 1 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Portland Sewage Plt, TN (2 mi away); precipitation: Portland Sewage Plt, TN (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

4 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

371197b

Mitchellville, TN · 4 mi

370487b

Cottontown, TN · 8 mi

370497b

Cross Plains, TN · 10 mi

White House, TN · 12 mi

Tennessee planting zones →

Questions about 37148

What planting zone is ZIP code 37148?

ZIP code 37148 (Portland, TN) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Portland, TN?

The median last spring frost (32 °F) near 37148 is April 5; after April 19 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Portland Sewage Plt station.

When is the first frost in Portland, TN?

The median first fall frost near 37148 is November 1, giving a median frost-free growing season of 210 days.

When should I plant tomatoes in 37148?

Start tomato seeds indoors around Feb 8 – Feb 22 and set transplants outside around Apr 12 – Apr 26, one to three weeks after the median last frost.

How much rain and snow does 37148 get?

About 54.3 inches of precipitation a year and 2 inches of snowfall (NOAA 1991–2020 normals, Portland Sewage Plt station).

How hot do summers get in Portland, TN?

The average high peaks at 89 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 37148 have?

The USDA soil survey maps Bewleyville at the center of ZIP 37148: silty clay loam, well drained, pH about 5.5 (moderately acidic).

Did spring come early in Portland, TN in 2026?

Spring leaf-out near 37148 came on Feb 25 in 2026, 4 days earlier than the 1991–2020 average (Mar 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Portland, TN?

Intermediate onions: the longest day near 37148 is 14 h 40 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 37148 change?

Yes. The 2012 USDA map put 37148 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.