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Frost dates and planting calendar for Knoxville, Tennessee

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
7b[1]
Median last spring frost
Apr 11[2]
Median first fall frost
Oct 28[3]
Growing season, median
198 days[4]

Knoxville, Tennessee is in USDA hardiness zone 7b[1]. In half of years the last spring frost comes after April 11, which is the median[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Mar 26, half of years Apr 11, 1 in 10 years after Apr 29Last frostmedian Apr 11First fall frost: 9 in 10 years before Nov 9, half of years Oct 28, 1 in 10 years before Oct 13First frostmedian Oct 28Frost riskHardyHardy vegetables: plant Mar 14 to Mar 28Mar 14 to Mar 28Semi-hardySemi-hardy vegetables: plant Mar 28 to Apr 11Mar 28 to Apr 11TenderTender vegetables: plant around Apr 11around Apr 11Very tenderVery tender vegetables: plant from Apr 25from Apr 25
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

These frost dates come from NOAA climate normals for the Knoxville Experiment Station, 5 miles from the city center[5]. They use records from 1991 to 2020. The median last spring frost is April 11, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after April 29[2]. In the fall, the median first frost is October 28, and in 1 of 10 years it comes before October 13[3]. These are chances from past years, not a forecast, so any year can be earlier or later.

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after March 26 after April 11 after April 29
First fall frost (32°F)[3] before October 13 before October 28 before November 9
  • Hard freeze (28°F): median last spring date March 31, median first fall date November 6[7].
  • Frost-free growing season: at least 176 days in 9 of 10 years, 198 days in half of years and 220 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Knoxville Experiment Station (USC00404946), 5 miles from the city center, 830 feet, 30 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension wrote its planting guide for Colorado, so the rules are applied here as a simple calculation[6]. Hardy vegetables like lettuce, peas and spinach can go in as early as 2 to 4 weeks before the median last frost, which works out to March 14 to March 28[6]. Semi-hardy vegetables like carrots and potatoes can go in as early as 2 weeks before the median last frost, March 28[9]. Tender vegetables like snap beans and sweet corn can be seeded from around the median last frost, April 11[10]. Very tender vegetables like tomatoes and peppers typically start 2 or more weeks after the median last frost, with April 25 as the earliest start[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 11) is March 14 to March 28[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 11) is March 28, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 11[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 11), is April 25[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 14 May 18 (from transplants)
Cabbage (hardy)[12] Mar 14 Jun 7 (from transplants)
Kohlrabi (hardy)[12] Mar 14 May 3
Lettuce (hardy)[12] Mar 14 May 13
Onions (hardy)[12] Mar 14 Jul 2
Peas (hardy)[12] Mar 14 May 18
Radishes (hardy)[12] Mar 14 Apr 13
Spinach (hardy)[12] Mar 14 Apr 23
Turnips (hardy)[12] Mar 14 May 3
Beets (semi-hardy)[12] Mar 28 May 27
Carrots (semi-hardy)[12] Mar 28 Jun 6
Cauliflower (semi-hardy)[12] Mar 28 not listed
Parsnips (semi-hardy)[12] Mar 28 Jun 6
Potatoes (semi-hardy)[12] Mar 28 Jul 31
Swiss chard (semi-hardy)[12] Mar 28 May 27
Snap beans (tender)[12] Apr 11 Jun 10
Sweet corn (tender)[12] Apr 11 Jun 10
Cucumbers (tender)[12] Apr 11 Jun 5
Summer squash (tender)[12] Apr 11 May 31
Cantaloupe (very tender)[12] Apr 25 Jul 19
Eggplant (very tender)[12] Apr 25 Jun 24 (from transplants)
Peppers (very tender)[12] Apr 25 Jul 4 (from transplants)
Tomatoes (very tender)[12] Apr 25 Jun 29 (from transplants)
Winter squash (very tender)[12] Apr 25 Aug 3
Watermelon (very tender)[12] Apr 25 Jul 19
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

Zone 7b means an average yearly coldest night of 5°F to 10°F over 1991 to 2020[1]. The zone is based on winter lows, not on summer heat or frost dates[14]. By land area, all of Knoxville lies in ZIP code areas rated zone 7b[15].

Zone 7b: average annual extreme minimum temperature 5°F to 10°F (1991 to 2020)[1]. Modeled value at the city center: 8.4°F[1].

Share of the city's land area by ZIP code zone: zone 7b 100%[15].

All towns in zone 7b and what zone 7b means

Zone by ZIP code
ZIP code Zone Coldest night range
37920[15] 7b 5 to 10°F
37921[15] 7b 5 to 10°F
37919[15] 7b 5 to 10°F
37914[15] 7b 5 to 10°F
37917[15] 7b 5 to 10°F
37912[15] 7b 5 to 10°F
37918[15] 7b 5 to 10°F
37909[15] 7b 5 to 10°F
37924[15] 7b 5 to 10°F
37922[15] 7b 5 to 10°F
37923[15] 7b 5 to 10°F
37915[15] 7b 5 to 10°F
37916[15] 7b 5 to 10°F
37932[15] 7b 5 to 10°F
37902[15] 7b 5 to 10°F
37934[15] 7b 5 to 10°F
37871[15] 7b 5 to 10°F
37849[15] 7b 5 to 10°F
37931[15] 7b 5 to 10°F
37929[15] 7b 5 to 10°F

Questions people ask

What growing zone is Knoxville, Tennessee?
The 2023 USDA map puts the center of Knoxville in zone 7b[1]. All of the city by land area is in ZIP code areas rated 7b[15].
When is the last frost in Knoxville?
The median last spring frost is April 11 at the NOAA station, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after April 29[2].
When to plant tomatoes in Knoxville?
CSU Extension says very tender vegetables like tomatoes typically go in 2 or more weeks after the average last frost[11]. Using the median last frost, the earliest start is April 25[11].
When is the first frost in Knoxville?
The median first fall frost is October 28, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before October 13[3].
How long is the growing season in Knoxville?
The growing season is at least 198 days in half of years[4]. It is at least 176 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Knoxville, Tennessee in zone 7b. Zone 7b means an average annual extreme minimum temperature of 5°F to 10°F over 1991 to 2020. The map's modeled value at the city center is 8.4°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after March 26, in half of years after April 11, and in 1 of 10 years after April 29 (NOAA 1991 to 2020 normals). The median last frost date is April 11. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before October 13, in half of years before October 28, and in 9 of 10 years before November 9 (NOAA 1991 to 2020 normals). The median first frost date is October 28. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 176 days in 9 of 10 years, at least 198 days in half of years, and at least 220 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Knoxville Experiment Station weather station (USC00404946), 5 miles from the center of Knoxville at 830 feet, using 30 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is March 31 and the median first fall date is November 6. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Knoxville, Tennessee overlaps 20 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 7b. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.