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

Planting zone for 37650 — Erwin, TN

ZIP code 37650 (Erwin, Unicoi County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 21 and the first fall frost October 23.

Where ZIP 37650 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 21
First frostOct 23
2012 zone7a

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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Erwin, 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 Erwin, TN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 21median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 23median — 10% chance by Oct 11
Growing season183 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 7 and returns around November 1.

From the NOAA station Erwin 1 W, TN — 4 miles away, elevation 1,719 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 37650

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 10 – Mar 24
SpinachSow outdoors · Mar 10 – Mar 31
Broccoli, cabbageStart indoors · Feb 10 – Feb 24
Broccoli, cabbageTransplant · Mar 31 – Apr 14
Onion setsPlant outdoors · Mar 24 – Apr 7
PotatoesPlant outdoors · Mar 31 – Apr 14
LettuceSow outdoors · Mar 24 – Apr 7
Carrots, beetsSow outdoors · Mar 31 – Apr 14
TomatoesStart indoors · Feb 24 – Mar 10
TomatoesTransplant · Apr 28 – May 12
Peppers, eggplantStart indoors · Feb 10 – Feb 24
Peppers, eggplantTransplant · May 5 – May 19
BeansSow outdoors · Apr 28 – May 12
Sweet cornSow outdoors · Apr 28 – May 12
Cucumbers, squashSow outdoors · Apr 28 – May 12
Fall lettuce, spinachSow outdoors · Aug 28 – Sep 11
GarlicPlant cloves · Oct 9 – Nov 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 21) and first fall frost (Oct 23) 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 37650 came on Mar 3 — 6 days earlier than the 1991–2020 average (Mar 9).

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).

Soil in Erwin, TN

The soil mapped at the center of ZIP 37650 is Unicoi — cobbly sandy loam, somewhat excessively drained.

TextureCobbly sandy loamdrains and warms fast; dries out and needs more feeding
pH4.6strongly acidic; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter4%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Unicoi-Rock outcrop complex, 50 to 80 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 37650; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Erwin, TN

Summer high85 °Faverage high, July
Winter low25 °Faverage low, January
Hot days18days a year at 90 °F or more
Freezing nights98nights a year at 32 °F or less
Growing degree days3,607base 50 °F — the season’s usable heat
Longest day14 h 37 mindaylight on June 21
Shortest day9 h 42 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation47 inper year, rain and melted snow
Snowfall9 inper year; 6 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 47 °F, low 25 °F 47°25° JanFebruary: average high 51 °F, low 27 °F 51°27° FebMarch: average high 59 °F, low 33 °F 59°33° MarApril: average high 68 °F, low 41 °F 68°41° AprMay: average high 76 °F, low 50 °F 76°50° MayJune: average high 83 °F, low 58 °F 83°58° JunJuly: average high 85 °F, low 62 °F 85°62° JulAugust: average high 85 °F, low 61 °F 85°61° AugSeptember: average high 80 °F, low 55 °F 80°55° SepOctober: average high 70 °F, low 43 °F 70°43° OctNovember: average high 59 °F, low 33 °F 59°33° NovDecember: average high 50 °F, low 28 °F 50°28° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.46 in precipitation, 3.4 in snowfall 3.5❄3 JanFebruary: 3.27 in precipitation, 2.5 in snowfall 3.3❄3 FebMarch: 3.82 in precipitation, 0.9 in snowfall 3.8❄1 MarApril: 3.99 in precipitation 4.0 AprMay: 4.83 in precipitation 4.8 MayJune: 5.07 in precipitation 5.1 JunJuly: 5.51 in precipitation 5.5 JulAugust: 4.76 in precipitation 4.8 AugSeptember: 3.28 in precipitation 3.3 SepOctober: 2.54 in precipitation 2.5 OctNovember: 2.83 in precipitation, 0.1 in snowfall 2.8 NovDecember: 3.64 in precipitation, 2.4 in snowfall 3.6❄2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Erwin 1 W, TN (4 mi away); precipitation: Erwin 1 W, TN (4 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.

376577a
Flag Pond, TN · 7 mi
287407a
Green Mountain, NC · 10 mi
376927a
Unicoi, TN · 11 mi
376907b
Telford, TN · 12 mi
376027b
Johnson City, TN · 13 mi
376417a
Chuckey, TN · 13 mi
376597a
Jonesborough, TN · 13 mi
376817b
Limestone, TN · 14 mi

Tennessee planting zones →

Questions about 37650

What planting zone is ZIP code 37650?

ZIP code 37650 (Erwin, 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 Erwin, TN?

The median last spring frost (32 °F) near 37650 is April 21; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Erwin 1 W station.

When is the first frost in Erwin, TN?

The median first fall frost near 37650 is October 23, giving a median frost-free growing season of 183 days.

When should I plant tomatoes in 37650?

Start tomato seeds indoors around Feb 24 – Mar 10 and set transplants outside around Apr 28 – May 12, one to three weeks after the median last frost.

How much rain and snow does 37650 get?

About 47 inches of precipitation a year and 9 inches of snowfall (NOAA 1991–2020 normals, Erwin 1 W station).

How hot do summers get in Erwin, TN?

The average high peaks at 85 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 37650 have?

The USDA soil survey maps Unicoi at the center of ZIP 37650: cobbly sandy loam, somewhat excessively drained, pH about 4.6 (strongly acidic).

Did spring come early in Erwin, TN in 2026?

Spring leaf-out near 37650 came on Mar 3 in 2026, 6 days earlier than the 1991–2020 average (Mar 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Erwin, TN?

Intermediate onions: the longest day near 37650 is 14 h 37 min, so day-neutral types bulb best; long-day varieties may not bulb fully.