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

Planting zone for 37870 — Speedwell, TN

ZIP code 37870 (Speedwell, Claiborne County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 23 and the first fall frost October 19.

Where ZIP 37870 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.

Zone7a0 to 5 °F

Coldest night−17.8 to −15 °C

Last frostApr 23

First frostOct 19

2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Speedwell, 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 Speedwell, TN

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 23median — 50% chance of a later frost

Safe for tender plantsMay 11only 10% chance of frost after

First fall frostOctober 19median — 10% chance by Oct 8

Growing season177 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 10 and returns around October 28.

From the NOAA station Tazewell, TN — 15 miles away, elevation 1,365 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 37870

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 12 – Mar 26

SpinachSow outdoors · Mar 12 – Apr 2

Broccoli, cabbageStart indoors · Feb 12 – Feb 26

Broccoli, cabbageTransplant · Apr 2 – Apr 16

Onion setsPlant outdoors · Mar 26 – Apr 9

PotatoesPlant outdoors · Apr 2 – Apr 16

LettuceSow outdoors · Mar 26 – Apr 9

Carrots, beetsSow outdoors · Apr 2 – Apr 16

TomatoesStart indoors · Feb 26 – Mar 12

TomatoesTransplant · Apr 30 – May 14

Peppers, eggplantStart indoors · Feb 12 – Feb 26

Peppers, eggplantTransplant · May 7 – May 21

BeansSow outdoors · Apr 30 – May 14

Sweet cornSow outdoors · Apr 30 – May 14

Cucumbers, squashSow outdoors · Apr 30 – May 14

Fall lettuce, spinachSow outdoors · Aug 24 – Sep 7

GarlicPlant cloves · Oct 5 – Nov 9

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 23) and first fall frost (Oct 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 37870 came on Feb 26 — 6 days earlier than the 1991–2020 average (Mar 4).

average
Mar 42026
Feb 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 7a in Tennessee

560 plants native to the lower 48 states, recorded in Tennessee, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. 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 Speedwell, TN.

Soil in Speedwell, TN

The soil mapped at the center of ZIP 37870 is Talbott — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH5.6moderately acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.25%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Rolling stony land (Talbott soil material).

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 37870; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Speedwell, TN

Summer high85 °Faverage high, July

Winter low23 °Faverage low, January

Hot days19days a year at 90 °F or more

Freezing nights115nights a year at 32 °F or less

Growing degree days3,464base 50 °F — the season’s usable heat

Longest day14 h 39 mindaylight on June 21

Shortest day9 h 40 mindaylight on December 21

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

Precipitation53.4 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Tazewell, TN (15 mi away); precipitation: Maynardville 0.6 E, TN (15 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

378517b

Pruden, TN · 7 mi

378667b

Sharps Chapel, TN · 8 mi

377247a

Cumberland Gap, TN · 9 mi

378257a

New Tazewell, TN · 9 mi

377157a

Clairfield, TN · 9 mi

Tennessee planting zones →

Questions about 37870

What planting zone is ZIP code 37870?

ZIP code 37870 (Speedwell, TN) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Speedwell, TN?

The median last spring frost (32 °F) near 37870 is April 23; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Tazewell station.

When is the first frost in Speedwell, TN?

The median first fall frost near 37870 is October 19, giving a median frost-free growing season of 177 days.

When should I plant tomatoes in 37870?

Start tomato seeds indoors around Feb 26 – Mar 12 and set transplants outside around Apr 30 – May 14, one to three weeks after the median last frost.

How much rain and snow does 37870 get?

About 53.4 inches of precipitation a year (NOAA 1991–2020 normals, Maynardville 0.6 E station).

How hot do summers get in Speedwell, TN?

The average high peaks at 85 °F in July, with about 19 days a year at 90 °F or more.

What kind of soil does 37870 have?

The USDA soil survey maps Talbott at the center of ZIP 37870: silt loam, well drained, pH about 5.6 (moderately acidic).

Did spring come early in Speedwell, TN in 2026?

Spring leaf-out near 37870 came on Feb 26 in 2026, 6 days earlier than the 1991–2020 average (Mar 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Speedwell, TN?

Intermediate onions: the longest day near 37870 is 14 h 39 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 37870 change?

Yes. The 2012 USDA map put 37870 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.