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

Planting zone for 37874 — Sweetwater, TN

ZIP code 37874 (Sweetwater, Monroe County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 10 and the first fall frost October 27.

Where ZIP 37874 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 10
First frostOct 27
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 Sweetwater, 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 Sweetwater, TN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 10median — 50% chance of a later frost
Safe for tender plantsApril 28only 10% chance of frost after
First fall frostOctober 27median — 10% chance by Oct 14
Growing season199 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 30 and returns around November 5.

From the NOAA station Decatur 7ne, TN — 12 miles away, elevation 751 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 37874

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 27 – Mar 13
SpinachSow outdoors · Feb 27 – Mar 20
Broccoli, cabbageStart indoors · Jan 30 – Feb 13
Broccoli, cabbageTransplant · Mar 20 – Apr 3
Onion setsPlant outdoors · Mar 13 – Mar 27
PotatoesPlant outdoors · Mar 20 – Apr 3
LettuceSow outdoors · Mar 13 – Mar 27
Carrots, beetsSow outdoors · Mar 20 – Apr 3
TomatoesStart indoors · Feb 13 – Feb 27
TomatoesTransplant · Apr 17 – May 1
Peppers, eggplantStart indoors · Jan 30 – Feb 13
Peppers, eggplantTransplant · Apr 24 – May 8
BeansSow outdoors · Apr 17 – May 1
Sweet cornSow outdoors · Apr 17 – May 1
Cucumbers, squashSow outdoors · Apr 17 – May 1
Fall lettuce, spinachSow outdoors · Sep 1 – Sep 15
GarlicPlant cloves · Oct 13 – Nov 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 10) and first fall frost (Oct 27) 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 37874 came on Feb 21 — about the same time as the 1991–2020 average (Feb 23).

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 Sweetwater, TN

The soil mapped at the center of ZIP 37874 is Decatur — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH5.3strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.25%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Decatur silt loam, 5 to 12 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 37874; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Sweetwater, TN

Summer high89 °Faverage high, July
Winter low28 °Faverage low, January
Hot days46days a year at 90 °F or more
Freezing nights99nights a year at 32 °F or less
Growing degree days4,386base 50 °F — the season’s usable heat
Longest day14 h 34 mindaylight on June 21
Shortest day9 h 45 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation58.8 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 48 °F, low 28 °F 48°28° JanFebruary: average high 53 °F, low 30 °F 53°30° FebMarch: average high 62 °F, low 36 °F 62°36° MarApril: average high 71 °F, low 44 °F 71°44° AprMay: average high 79 °F, low 54 °F 79°54° MayJune: average high 86 °F, low 63 °F 86°63° JunJuly: average high 89 °F, low 67 °F 89°67° JulAugust: average high 89 °F, low 66 °F 89°66° AugSeptember: average high 84 °F, low 59 °F 84°59° SepOctober: average high 73 °F, low 46 °F 73°46° OctNovember: average high 61 °F, low 35 °F 61°35° NovDecember: average high 51 °F, low 30 °F 51°30° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 5.85 in precipitation 5.8 JanFebruary: 5.30 in precipitation 5.3 FebMarch: 5.40 in precipitation 5.4 MarApril: 5.45 in precipitation 5.5 AprMay: 4.79 in precipitation 4.8 MayJune: 4.55 in precipitation 4.5 JunJuly: 5.35 in precipitation 5.3 JulAugust: 3.59 in precipitation 3.6 AugSeptember: 4.48 in precipitation 4.5 SepOctober: 3.42 in precipitation 3.4 OctNovember: 4.69 in precipitation 4.7 NovDecember: 5.93 in precipitation 5.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Decatur 7ne, TN (12 mi away); precipitation: Rockwood 11.3 S, TN (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7b.

378467b
Philadelphia, TN · 6 mi
378267b
Niota, TN · 8 mi
373547b
Madisonville, TN · 9 mi
377747b
Loudon, TN · 11 mi
373717b
Athens, TN · 13 mi
378807b
Ten Mile, TN · 13 mi
373297b
Englewood, TN · 14 mi
373037b
Athens, TN · 15 mi

Tennessee planting zones →

Questions about 37874

What planting zone is ZIP code 37874?

ZIP code 37874 (Sweetwater, 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 Sweetwater, TN?

The median last spring frost (32 °F) near 37874 is April 10; after April 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Decatur 7ne station.

When is the first frost in Sweetwater, TN?

The median first fall frost near 37874 is October 27, giving a median frost-free growing season of 199 days.

When should I plant tomatoes in 37874?

Start tomato seeds indoors around Feb 13 – Feb 27 and set transplants outside around Apr 17 – May 1, one to three weeks after the median last frost.

How much rain and snow does 37874 get?

About 58.8 inches of precipitation a year (NOAA 1991–2020 normals, Rockwood 11.3 S station).

How hot do summers get in Sweetwater, TN?

The average high peaks at 89 °F in July, with about 46 days a year at 90 °F or more.

What kind of soil does 37874 have?

The USDA soil survey maps Decatur at the center of ZIP 37874: silt loam, well drained, pH about 5.3 (strongly acidic).

Did spring come early in Sweetwater, TN in 2026?

Spring leaf-out near 37874 came on Feb 21 in 2026, about the same as the 1991–2020 average (Feb 23), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Sweetwater, TN?

Intermediate onions: the longest day near 37874 is 14 h 34 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 37874 change?

Yes. The 2012 USDA map put 37874 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.