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Frost dates and planting calendar for Worcester, Massachusetts

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

USDA hardiness zone
6a[1]
Median last spring frost
Apr 23[2]
Median first fall frost
Oct 21[3]
Growing season, median
181 days[4]

Worcester, Massachusetts is in USDA hardiness zone 6a at the city center[1]. In half of years the last spring frost comes after April 23, which is the median[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 11, half of years Apr 23, 1 in 10 years after May 5Last frostmedian Apr 23First fall frost: 9 in 10 years before Nov 3, half of years Oct 21, 1 in 10 years before Oct 6First frostmedian Oct 21Frost riskHardyHardy vegetables: plant Mar 26 to Apr 9Mar 26 to Apr 9Semi-hardySemi-hardy vegetables: plant Apr 9 to Apr 23Apr 9 to Apr 23TenderTender vegetables: plant around Apr 23around Apr 23Very tenderVery tender vegetables: plant from May 7from May 7
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 Worcester Regional Airport station, using records from 1991 to 2020[5]. In 9 of 10 years the last spring frost comes after April 11, and in 1 of 10 years it comes after May 5[2]. In the fall, the first frost comes before October 21 in half of years, and before November 3 in 9 of 10 years[3]. These are odds from past records, not a forecast, so any year can be earlier or later[5].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 11 after April 23 after May 5
First fall frost (32°F)[3] before October 6 before October 21 before November 3
  • Hard freeze (28°F): median last spring date April 11, median first fall date November 1[7].
  • Frost-free growing season: at least 160 days in 9 of 10 years, 181 days in half of years and 198 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: Worcester Regional Airport (USW00094746), 3.3 miles from the city center, 1,000 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 treat these dates as a starting point[6]. This page takes the NOAA median last frost, April 23, as the average last frost[6]. Hardy vegetables such as broccoli, lettuce, peas and spinach can go in as early as 2 to 4 weeks before that date, which is March 26 to April 9[6]. Semi-hardy vegetables such as beets, carrots and potatoes can go in as early as 2 weeks before, which is April 9[9]. Tender vegetables such as snap beans and sweet corn can be seeded around April 23[10]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the last frost, so the earliest start is May 7[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 23) is March 26 to April 9[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 23) is April 9, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 23[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 23), is May 7[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 26 May 30 (from transplants)
Cabbage (hardy)[12] Mar 26 Jun 19 (from transplants)
Kohlrabi (hardy)[12] Mar 26 May 15
Lettuce (hardy)[12] Mar 26 May 25
Onions (hardy)[12] Mar 26 Jul 14
Peas (hardy)[12] Mar 26 May 30
Radishes (hardy)[12] Mar 26 Apr 25
Spinach (hardy)[12] Mar 26 May 5
Turnips (hardy)[12] Mar 26 May 15
Beets (semi-hardy)[12] Apr 9 Jun 8
Carrots (semi-hardy)[12] Apr 9 Jun 18
Cauliflower (semi-hardy)[12] Apr 9 not listed
Parsnips (semi-hardy)[12] Apr 9 Jun 18
Potatoes (semi-hardy)[12] Apr 9 Aug 12
Swiss chard (semi-hardy)[12] Apr 9 Jun 8
Snap beans (tender)[12] Apr 23 Jun 22
Sweet corn (tender)[12] Apr 23 Jun 22
Cucumbers (tender)[12] Apr 23 Jun 17
Summer squash (tender)[12] Apr 23 Jun 12
Cantaloupe (very tender)[12] May 7 Jul 31
Eggplant (very tender)[12] May 7 Jul 6 (from transplants)
Peppers (very tender)[12] May 7 Jul 16 (from transplants)
Tomatoes (very tender)[12] May 7 Jul 11 (from transplants)
Winter squash (very tender)[12] May 7 Aug 15
Watermelon (very tender)[12] May 7 Jul 31
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 6a means the coldest night of each winter averages -10°F to -5°F over 1991 to 2020[1]. The zone is based on winter lows, not on summer heat or frost dates[14]. Worcester is not all one zone. By land area, 59% lies in ZIP code areas rated 6a and 41% in areas rated 6b[15].

Zone 6a: average annual extreme minimum temperature -10°F to -5°F (1991 to 2020)[1]. Modeled value at the city center: -5.2°F[1].

Share of the city's land area by ZIP code zone: zone 6a 59%, zone 6b 41%[15].

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

Zone by ZIP code
ZIP code Zone Coldest night range
01604[15] 6a -10 to -5°F
01602[15] 6b -5 to 0°F
01605[15] 6a -10 to -5°F
01606[15] 6b -5 to 0°F
01603[15] 6a -10 to -5°F
01609[15] 6b -5 to 0°F
01607[15] 6a -10 to -5°F
01610[15] 6a -10 to -5°F
01608[15] 6a -10 to -5°F
01545[15] 6a -10 to -5°F
01583[15] 6a -10 to -5°F

Questions people ask

What growing zone is Worcester, Massachusetts?
The center of Worcester is in USDA zone 6a[1]. By land area, 59% of the city is in 6a ZIP code areas and 41% is in 6b areas[15].
When is the last frost in Worcester?
The median last spring frost at the Worcester Regional Airport station is April 23, 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 is the first frost in Worcester?
In half of years the first fall frost comes before October 21, and in 9 of 10 years it comes before November 3[3].
When to plant tomatoes in Worcester?
Colorado State University Extension says tomatoes are very tender and typically go in 2 or more weeks after the average last frost[11]. Using the median last frost, the earliest start is May 7[11].
How long is the growing season in Worcester?
The growing season is at least 181 days in half of years[4]. It is at least 160 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Worcester, Massachusetts in zone 6a. Zone 6a means an average annual extreme minimum temperature of -10°F to -5°F over 1991 to 2020. The map's modeled value at the city center is minus 5.2°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 11, in half of years after April 23, and in 1 of 10 years after May 5 (NOAA 1991 to 2020 normals). The median last frost date is April 23. 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 6, in half of years before October 21, and in 9 of 10 years before November 3 (NOAA 1991 to 2020 normals). The median first frost date is October 21. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 160 days in 9 of 10 years, at least 181 days in half of years, and at least 198 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Worcester Regional Airport weather station (USW00094746), 3.3 miles from the center of Worcester at 1,000 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 11 and the median first fall date is November 1. 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. Worcester, Massachusetts overlaps 11 ZIP code areas. By land area, 59% lies in ZIP code areas rated zone 6a, 41% 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.