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Frost dates and planting calendar for Saginaw, Michigan

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 29[2]
Median first fall frost
Oct 21[3]
Growing season, median
175 days[4]

Saginaw, Michigan is in USDA hardiness zone 6a[1]. The median last spring frost is April 29, which means that in half of years the last frost comes after that date[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 14, half of years Apr 29, 1 in 10 years after May 13Last frostmedian Apr 29First fall frost: 9 in 10 years before Nov 2, half of years Oct 21, 1 in 10 years before Oct 5First frostmedian Oct 21Frost riskHardyHardy vegetables: plant Apr 1 to Apr 15Apr 1 to Apr 15Semi-hardySemi-hardy vegetables: plant Apr 15 to Apr 29Apr 15 to Apr 29TenderTender vegetables: plant around Apr 29around Apr 29Very tenderVery tender vegetables: plant from May 13from May 13
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 Saginaw #3 weather station, using records from 1991 to 2020[5]. In 9 of 10 years the last spring frost comes after April 14, and in 1 of 10 years it comes after May 13[2]. In the fall, the first frost comes before October 5 in 1 of 10 years, and before November 2 in 9 of 10 years[3]. The median first fall frost is October 21[3]. These are chances from past records and not a forecast, so any year can come 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 14 after April 29 after May 13
First fall frost (32°F)[3] before October 5 before October 21 before November 2
  • Hard freeze (28°F): median last spring date April 17, median first fall date November 3[7].
  • Frost-free growing season: at least 155 days in 9 of 10 years, 175 days in half of years and 194 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: Saginaw #3 (USC00207222), 0.6 miles from the city center, 600 feet, 18 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension groups vegetables by how well they handle cold, and its guide was written for Colorado[6]. GardenFacts used the NOAA median last frost of April 29 as the average last frost for Saginaw[6]. Hardy vegetables such as peas, spinach and lettuce can go in as early as 2 to 4 weeks before that date, which is April 1 to April 15[6]. Semi-hardy vegetables such as carrots and potatoes can go in as early as April 15, up to the median date itself[9]. Tender vegetables such as snap beans and sweet corn are planted from seed around April 29[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 13[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 29) is April 1 to April 15[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 29) is April 15, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 29[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 29), is May 13[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Apr 1 Jun 5 (from transplants)
Cabbage (hardy)[12] Apr 1 Jun 25 (from transplants)
Kohlrabi (hardy)[12] Apr 1 May 21
Lettuce (hardy)[12] Apr 1 May 31
Onions (hardy)[12] Apr 1 Jul 20
Peas (hardy)[12] Apr 1 Jun 5
Radishes (hardy)[12] Apr 1 May 1
Spinach (hardy)[12] Apr 1 May 11
Turnips (hardy)[12] Apr 1 May 21
Beets (semi-hardy)[12] Apr 15 Jun 14
Carrots (semi-hardy)[12] Apr 15 Jun 24
Cauliflower (semi-hardy)[12] Apr 15 not listed
Parsnips (semi-hardy)[12] Apr 15 Jun 24
Potatoes (semi-hardy)[12] Apr 15 Aug 18
Swiss chard (semi-hardy)[12] Apr 15 Jun 14
Snap beans (tender)[12] Apr 29 Jun 28
Sweet corn (tender)[12] Apr 29 Jun 28
Cucumbers (tender)[12] Apr 29 Jun 23
Summer squash (tender)[12] Apr 29 Jun 18
Cantaloupe (very tender)[12] May 13 Aug 6
Eggplant (very tender)[12] May 13 Jul 12 (from transplants)
Peppers (very tender)[12] May 13 Jul 22 (from transplants)
Tomatoes (very tender)[12] May 13 Jul 17 (from transplants)
Winter squash (very tender)[12] May 13 Aug 21
Watermelon (very tender)[12] May 13 Aug 6
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 the winter averages between minus 10°F and minus 5°F, based on 1991 to 2020[1]. The zone is about winter lows. It does not describe summer heat or frost dates[14]. USDA describes the map as the standard gardeners use to judge which perennial plants are most likely to thrive[14]. All of Saginaw's land area lies in ZIP code areas rated zone 6a[15].

Zone 6a: average annual extreme minimum temperature -10°F to -5°F (1991 to 2020)[1]. Modeled value at the city center: -6.6°F[1].

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

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

Zone by ZIP code
ZIP code Zone Coldest night range
48601[15] 6a -10 to -5°F
48602[15] 6a -10 to -5°F
48607[15] 6a -10 to -5°F
48604[15] 6a -10 to -5°F
48638[15] 6a -10 to -5°F
48603[15] 6a -10 to -5°F

Questions people ask

What growing zone is Saginaw, Michigan?
The center of Saginaw is in USDA zone 6a on the 2023 map[1]. By land area, 100% of the city lies in ZIP code areas rated 6a[15].
When is the last frost in Saginaw?
The median last spring frost is April 29, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 13[2].
When to plant tomatoes in Saginaw?
CSU Extension says tomatoes are very tender and typically go in 2 or more weeks after the average last spring frost[11]. Using the median last frost, the earliest start is May 13[11].
When is the first frost in Saginaw?
The median first fall frost is October 21, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before October 5[3].
How long is the growing season in Saginaw?
The growing season is at least 175 days in half of years[4]. It is at least 155 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Saginaw, Michigan 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 6.6°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 14, in half of years after April 29, and in 1 of 10 years after May 13 (NOAA 1991 to 2020 normals). The median last frost date is April 29. 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 5, in half of years before October 21, and in 9 of 10 years before November 2 (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 155 days in 9 of 10 years, at least 175 days in half of years, and at least 194 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Saginaw #3 weather station (USC00207222), 0.6 miles from the center of Saginaw at 600 feet, using 18 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 17 and the median first fall date is November 3. 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. Saginaw, Michigan overlaps 6 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 6a. 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.