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Frost dates and planting calendar for Hartford, Connecticut

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 17[2]
Median first fall frost
Oct 26[3]
Growing season, median
191 days[4]

The USDA 2023 map puts the center of Hartford in zone 6b[1]. NOAA records from 1991 to 2020 show a median last spring frost of April 17[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 1, half of years Apr 17, 1 in 10 years after May 1Last frostmedian Apr 17First fall frost: 9 in 10 years before Nov 7, half of years Oct 26, 1 in 10 years before Oct 12First frostmedian Oct 26Frost riskHardyHardy vegetables: plant Mar 20 to Apr 3Mar 20 to Apr 3Semi-hardySemi-hardy vegetables: plant Apr 3 to Apr 17Apr 3 to Apr 17TenderTender vegetables: plant around Apr 17around Apr 17Very tenderVery tender vegetables: plant from May 1from May 1
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)[7]. Exact dates are in the tables below.

These dates come from NOAA climate normals for the Hartford Brainard Field weather station, using 1991 to 2020 records[5]. In half of years the last spring frost comes after April 17, and in 1 of 10 years it comes after May 1[2]. In half of years the first fall frost comes before October 26, and in 1 of 10 years it comes before October 12[3]. These are chances, not promises, and any year can be earlier or later[5]. At this station the low reached 32°F or colder in 100% of years[6].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 1 after April 17 after May 1
First fall frost (32°F)[3] before October 12 before October 26 before November 7
  • Hard freeze (28°F): median last spring date April 3, median first fall date November 5[8].
  • Frost-free growing season: at least 169 days in 9 of 10 years, 191 days in half of years and 212 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[6].
  • Weather station: Hartford Brainard Field (USW00014752), 2.6 miles from the city center, 19 feet, 28 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension wrote its vegetable planting guide for Colorado, so treat these dates as a starting point[7]. We took the NOAA median last frost of April 17 as the average last frost[7]. Hardy vegetables such as broccoli, lettuce and peas can go in as early as 2 to 4 weeks before it, which is March 20 to April 3[7]. Semi-hardy vegetables such as carrots and potatoes can go in as early as 2 weeks before it, which is April 3[9]. Tender vegetables such as snap beans and sweet corn can start from seed around April 17[10]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after it, so the earliest start is May 1[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 17) is March 20 to April 3[7]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 17) is April 3, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 17[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 17), is May 1[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 20 May 24 (from transplants)
Cabbage (hardy)[12] Mar 20 Jun 13 (from transplants)
Kohlrabi (hardy)[12] Mar 20 May 9
Lettuce (hardy)[12] Mar 20 May 19
Onions (hardy)[12] Mar 20 Jul 8
Peas (hardy)[12] Mar 20 May 24
Radishes (hardy)[12] Mar 20 Apr 19
Spinach (hardy)[12] Mar 20 Apr 29
Turnips (hardy)[12] Mar 20 May 9
Beets (semi-hardy)[12] Apr 3 Jun 2
Carrots (semi-hardy)[12] Apr 3 Jun 12
Cauliflower (semi-hardy)[12] Apr 3 not listed
Parsnips (semi-hardy)[12] Apr 3 Jun 12
Potatoes (semi-hardy)[12] Apr 3 Aug 6
Swiss chard (semi-hardy)[12] Apr 3 Jun 2
Snap beans (tender)[12] Apr 17 Jun 16
Sweet corn (tender)[12] Apr 17 Jun 16
Cucumbers (tender)[12] Apr 17 Jun 11
Summer squash (tender)[12] Apr 17 Jun 6
Cantaloupe (very tender)[12] May 1 Jul 25
Eggplant (very tender)[12] May 1 Jun 30 (from transplants)
Peppers (very tender)[12] May 1 Jul 10 (from transplants)
Tomatoes (very tender)[12] May 1 Jul 5 (from transplants)
Winter squash (very tender)[12] May 1 Aug 9
Watermelon (very tender)[12] May 1 Jul 25
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 6b means an average yearly coldest night of -5°F to 0°F over 1991 to 2020[1]. The zone is based on that coldest winter night, not on frost dates[14]. All of Hartford's land area 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: -0.4°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
06106[15] 6b -5 to 0°F
06114[15] 6b -5 to 0°F
06120[15] 6b -5 to 0°F
06112[15] 6b -5 to 0°F
06105[15] 6b -5 to 0°F
06103[15] 6b -5 to 0°F
06110[15] 6b -5 to 0°F
06095[15] 6b -5 to 0°F

Questions people ask

What growing zone is Hartford, Connecticut?
The 2023 USDA map puts the center of Hartford in zone 6b[1]. By land area, 100% of the city lies in ZIP code areas rated zone 6b[15].
When is the last frost in Hartford?
The median last spring frost is April 17 at the Hartford Brainard Field station, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 1[2].
When to plant tomatoes in Hartford?
CSU Extension lists tomatoes as very tender and typically 2 or more weeks after the average last spring frost[11]. Using the median last frost, the earliest start is May 1[11].
When is the first frost in Hartford?
The median first fall frost is October 26, so in half of years it comes before that date[3]. In 1 of 10 years it comes before October 12[3].
How long is the growing season in Hartford?
The season between the last spring and first fall frost is at least 191 days in half of years[4]. It is at least 169 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Hartford, Connecticut 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 0.4°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 April 1, in half of years after April 17, and in 1 of 10 years after May 1 (NOAA 1991 to 2020 normals). The median last frost date is April 17. 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 12, in half of years before October 26, and in 9 of 10 years before November 7 (NOAA 1991 to 2020 normals). The median first frost date is October 26. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 169 days in 9 of 10 years, at least 191 days in half of years, and at least 212 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Hartford Brainard Field weather station (USW00014752), 2.6 miles from the center of Hartford at 19 feet, using 28 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. 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
  7. 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
  8. Hard freeze (28°F) at this station: the median last spring date is April 3 and the median first fall date is November 5. 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. Hartford, Connecticut overlaps 8 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.