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Frost dates and planting calendar for Dayton, Ohio

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

USDA hardiness zone
6b[1]
Median last spring frost
Apr 18[2]
Median first fall frost
Oct 25[3]
Growing season, median
189 days[4]

Dayton, Ohio is in USDA hardiness zone 6b at the city center[1]. The median last spring frost at the nearby NOAA station is April 18[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 3, half of years Apr 18, 1 in 10 years after May 5Last frostmedian Apr 18First fall frost: 9 in 10 years before Nov 7, half of years Oct 25, 1 in 10 years before Oct 13First frostmedian Oct 25Frost riskHardyHardy vegetables: plant Mar 21 to Apr 4Mar 21 to Apr 4Semi-hardySemi-hardy vegetables: plant Apr 4 to Apr 18Apr 4 to Apr 18TenderTender vegetables: plant around Apr 18around Apr 18Very tenderVery tender vegetables: plant from May 2from May 2
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 Dayton Mcd weather station, using 1991 to 2020 records[5]. In half of years the last spring frost comes after April 18, and in 1 of 10 years it comes after May 5[2]. In half of years the first fall frost comes before October 25, and in 1 of 10 years it comes before October 13[3]. These are odds from past years, not a forecast, so any year can be earlier or later[2].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 3 after April 18 after May 5
First fall frost (32°F)[3] before October 13 before October 25 before November 7
  • Hard freeze (28°F): median last spring date April 6, median first fall date November 4[7].
  • Frost-free growing season: at least 168 days in 9 of 10 years, 189 days in half of years and 209 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: Dayton Mcd (USC00332067), 1.5 miles from the city center, 720 feet, 28 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension's planting guide was written for Colorado, so these dates are simple arithmetic from the Dayton median last frost of April 18[6]. CSU puts broccoli, cabbage, lettuce, peas and spinach in the hardy group, which can go in as early as 2 to 4 weeks before the median last frost, or March 21 to April 4[6]. Beets, carrots and potatoes are semi-hardy and can go in as early as 2 weeks before it, which is April 4[9]. Tomatoes, peppers and eggplant are very tender, and CSU says typically 2 or more weeks after the last frost, so the earliest start is May 2[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 18) is March 21 to April 4[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 18) is April 4, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 18[11]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 18), is May 2[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 21 May 25 (from transplants)
Cabbage (hardy)[12] Mar 21 Jun 14 (from transplants)
Kohlrabi (hardy)[12] Mar 21 May 10
Lettuce (hardy)[12] Mar 21 May 20
Onions (hardy)[12] Mar 21 Jul 9
Peas (hardy)[12] Mar 21 May 25
Radishes (hardy)[12] Mar 21 Apr 20
Spinach (hardy)[12] Mar 21 Apr 30
Turnips (hardy)[12] Mar 21 May 10
Beets (semi-hardy)[12] Apr 4 Jun 3
Carrots (semi-hardy)[12] Apr 4 Jun 13
Cauliflower (semi-hardy)[12] Apr 4 not listed
Parsnips (semi-hardy)[12] Apr 4 Jun 13
Potatoes (semi-hardy)[12] Apr 4 Aug 7
Swiss chard (semi-hardy)[12] Apr 4 Jun 3
Snap beans (tender)[12] Apr 18 Jun 17
Sweet corn (tender)[12] Apr 18 Jun 17
Cucumbers (tender)[12] Apr 18 Jun 12
Summer squash (tender)[12] Apr 18 Jun 7
Cantaloupe (very tender)[12] May 2 Jul 26
Eggplant (very tender)[12] May 2 Jul 1 (from transplants)
Peppers (very tender)[12] May 2 Jul 11 (from transplants)
Tomatoes (very tender)[12] May 2 Jul 6 (from transplants)
Winter squash (very tender)[12] May 2 Aug 10
Watermelon (very tender)[12] May 2 Jul 26
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

The 2023 USDA map puts the center of Dayton in zone 6b, which means an average coldest night of -5°F to 0°F over 1991 to 2020[1]. A zone is based on the coldest winter night, not on summer heat or frost dates[14]. By land area, 100% of Dayton lies in ZIP code areas rated zone 6b[15].

Zone 6b: average annual extreme minimum temperature -5°F to 0°F (1991 to 2020)[1]. Modeled value at the city center: -2.1°F[1].

Share of the city's land area by ZIP code zone: zone 6b 100%[15].

All towns in zone 6b and what zone 6b means

Zone by ZIP code
ZIP code Zone Coldest night range
45417[15] 6b -5 to 0°F
45404[15] 6b -5 to 0°F
45377[15] 6b -5 to 0°F
45414[15] 6b -5 to 0°F
45402[15] 6b -5 to 0°F
45406[15] 6b -5 to 0°F
45424[15] 6b -5 to 0°F
45403[15] 6b -5 to 0°F
45410[15] 6b -5 to 0°F
45405[15] 6b -5 to 0°F
45420[15] 6b -5 to 0°F
45426[15] 6b -5 to 0°F
45409[15] 6b -5 to 0°F
45432[15] 6b -5 to 0°F
45419[15] 6b -5 to 0°F
45428[15] 6b -5 to 0°F
45431[15] 6b -5 to 0°F
45416[15] 6b -5 to 0°F
45423[15] 6b -5 to 0°F
45324[15] 6b -5 to 0°F

Questions people ask

What growing zone is Dayton, Ohio?
The 2023 USDA map puts the center of Dayton in zone 6b[1]. All of the city's land area is in ZIP code areas rated 6b[15].
When is the last frost in Dayton?
The median last spring frost is April 18, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 5[2].
When to plant tomatoes in Dayton?
CSU says very tender crops like tomatoes typically go in 2 or more weeks after the average last frost, which gives May 2 as the earliest start[10]. CSU's guide was written for Colorado[10].
When is the first frost in Dayton?
The median first fall frost is October 25, so in half of years it comes before that date[3]. In 1 of 10 years it comes before October 13[3].
How long is the growing season in Dayton?
The growing season is at least 189 days in half of years[4]. It is at least 168 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Dayton, Ohio in zone 6b. Zone 6b means an average annual extreme minimum temperature of -5°F to 0°F over 1991 to 2020. The map's modeled value at the city center is minus 2.1°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 April 3, in half of years after April 18, and in 1 of 10 years after May 5 (NOAA 1991 to 2020 normals). The median last frost date is April 18. 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 25, and in 9 of 10 years before November 7 (NOAA 1991 to 2020 normals). The median first frost date is October 25. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 168 days in 9 of 10 years, at least 189 days in half of years, and at least 209 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Dayton Mcd weather station (USC00332067), 1.5 miles from the center of Dayton at 720 feet, using 28 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 April 6 and the median first fall date is November 4. 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 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
  11. 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
  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. Dayton, Ohio overlaps 20 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 6b. 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.