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Frost dates and planting calendar for Belleville, Illinois

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

USDA hardiness zone
7a[1]
Median last spring frost
Apr 12[2]
Median first fall frost
Oct 20[3]
Growing season, median
189 days[4]

Belleville, Illinois sits in USDA hardiness zone 7a on the 2023 map[1]. The median last spring frost is April 12, which means a last frost after that date in half of years[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Mar 28, half of years Apr 12, 1 in 10 years after Apr 28Last frostmedian Apr 12First fall frost: 9 in 10 years before Nov 1, half of years Oct 20, 1 in 10 years before Oct 3First frostmedian Oct 20Frost riskHardyHardy vegetables: plant Mar 15 to Mar 29Mar 15 to Mar 29Semi-hardySemi-hardy vegetables: plant Mar 29 to Apr 12Mar 29 to Apr 12TenderTender vegetables: plant around Apr 12around Apr 12Very tenderVery tender vegetables: plant from Apr 26from Apr 26
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 Belleville Siu Rsch weather station, using records from 1991 to 2020[5]. In 9 of 10 years the last spring frost comes after March 28, and in 1 of 10 years it comes after April 28[2]. In the fall, the first frost comes before October 3 in 1 of 10 years, and before November 1 in 9 of 10 years[3]. The median first fall frost is October 20[3]. These are odds from past records, 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 March 28 after April 12 after April 28
First fall frost (32°F)[3] before October 3 before October 20 before November 1
  • Hard freeze (28°F): median last spring date March 31, median first fall date October 30[7].
  • Frost-free growing season: at least 167 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: Belleville Siu Rsch (USW00013802), 7.7 miles from the city center, 450 feet, 26 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension's planting guide groups vegetables by how well they handle cold, and it was written for Colorado[6]. GardenFacts used the NOAA median last frost of April 12 as the average last frost[6]. Hardy vegetables such as lettuce, peas and spinach can go in as early as 2 to 4 weeks before that, which is March 15 to March 29[6]. Semi-hardy vegetables such as carrots and potatoes can go in as early as 2 weeks before, which is March 29[9]. Tender vegetables such as snap beans and sweet corn are sown from seed around April 12[10]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the median last frost, so the earliest start is April 26[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 12) is March 15 to March 29[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 12) is March 29, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 12[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 12), is April 26[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 15 May 19 (from transplants)
Cabbage (hardy)[12] Mar 15 Jun 8 (from transplants)
Kohlrabi (hardy)[12] Mar 15 May 4
Lettuce (hardy)[12] Mar 15 May 14
Onions (hardy)[12] Mar 15 Jul 3
Peas (hardy)[12] Mar 15 May 19
Radishes (hardy)[12] Mar 15 Apr 14
Spinach (hardy)[12] Mar 15 Apr 24
Turnips (hardy)[12] Mar 15 May 4
Beets (semi-hardy)[12] Mar 29 May 28
Carrots (semi-hardy)[12] Mar 29 Jun 7
Cauliflower (semi-hardy)[12] Mar 29 not listed
Parsnips (semi-hardy)[12] Mar 29 Jun 7
Potatoes (semi-hardy)[12] Mar 29 Aug 1
Swiss chard (semi-hardy)[12] Mar 29 May 28
Snap beans (tender)[12] Apr 12 Jun 11
Sweet corn (tender)[12] Apr 12 Jun 11
Cucumbers (tender)[12] Apr 12 Jun 6
Summer squash (tender)[12] Apr 12 Jun 1
Cantaloupe (very tender)[12] Apr 26 Jul 20
Eggplant (very tender)[12] Apr 26 Jun 25 (from transplants)
Peppers (very tender)[12] Apr 26 Jul 5 (from transplants)
Tomatoes (very tender)[12] Apr 26 Jun 30 (from transplants)
Winter squash (very tender)[12] Apr 26 Aug 4
Watermelon (very tender)[12] Apr 26 Jul 20
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 7a means an average yearly coldest night of 0°F to 5°F over 1991 to 2020[1]. The zone is based on winter lows, not on summer heat or frost dates[14]. All of the city's land area lies in ZIP code areas rated zone 7a, so Belleville does not span more than one zone[15].

Zone 7a: average annual extreme minimum temperature 0°F to 5°F (1991 to 2020)[1]. Modeled value at the city center: 1°F[1].

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

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

Zone by ZIP code
ZIP code Zone Coldest night range
62220[15] 7a 0 to 5°F
62223[15] 7a 0 to 5°F
62226[15] 7a 0 to 5°F
62221[15] 7a 0 to 5°F
62243[15] 7a 0 to 5°F
62207[15] 7a 0 to 5°F
62203[15] 7a 0 to 5°F

Questions people ask

What growing zone is Belleville, Illinois?
Belleville is in USDA zone 7a on the 2023 map[1]. All of its land area lies in ZIP code areas rated 7a[15].
When is the last frost in Belleville?
The median last spring frost is April 12, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after April 28[2].
When to plant tomatoes in Belleville?
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 26[11].
When is the first frost in Belleville?
The median first fall frost is October 20, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before October 3[3].
How long is the growing season in Belleville?
The growing season is at least 189 days in half of years[4]. It is at least 167 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Belleville, Illinois in zone 7a. Zone 7a means an average annual extreme minimum temperature of 0°F to 5°F over 1991 to 2020. The map's modeled value at the city center is 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 March 28, in half of years after April 12, and in 1 of 10 years after April 28 (NOAA 1991 to 2020 normals). The median last frost date is April 12. 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 3, in half of years before October 20, and in 9 of 10 years before November 1 (NOAA 1991 to 2020 normals). The median first frost date is October 20. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 167 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 Belleville Siu Rsch weather station (USW00013802), 7.7 miles from the center of Belleville at 450 feet, using 26 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 October 30. 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. Belleville, Illinois overlaps 7 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 7a. 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.