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Frost dates and planting calendar for Golden, Colorado

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
May 5[2]
Median first fall frost
Oct 5[3]
Growing season, median
151 days[4]

The center of Golden, Colorado is in USDA hardiness zone 6a[1]. The median last spring frost is May 5, 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 24, half of years May 5, 1 in 10 years after May 18Last frostmedian May 5First fall frost: 9 in 10 years before Oct 18, half of years Oct 5, 1 in 10 years before Sep 20First frostmedian Oct 5Frost riskHardyHardy vegetables: plant Apr 7 to Apr 21Apr 7 to Apr 21Semi-hardySemi-hardy vegetables: plant Apr 21 to May 5Apr 21 to May 5TenderTender vegetables: plant around May 5around May 5Very tenderVery tender vegetables: plant from May 19from May 19
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 Wheat Ridge 2 weather station[5]. In 9 of 10 years the last spring frost comes after April 24, and in 1 of 10 years it comes after May 18[2]. In half of years the first fall frost comes before October 5, and in 1 of 10 years it comes before September 20[3]. These are chances from 1991 to 2020 records, 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 24 after May 5 after May 18
First fall frost (32°F)[3] before September 20 before October 5 before October 18
  • Hard freeze (28°F): median last spring date April 25, median first fall date October 14[7].
  • Frost-free growing season: at least 132 days in 9 of 10 years, 151 days in half of years and 167 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: Wheat Ridge 2 (USC00058995), 5.5 miles from the city center, 5,398 feet, 28 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension's planting guide was written for Colorado[6]. It sorts vegetables into groups by how they handle frost. Hardy vegetables such as broccoli, lettuce, peas and spinach can go in as early as 2 to 4 weeks before the average last spring frost, which works out to April 7 to April 21 in Golden[6]. Semi-hardy vegetables such as carrots and potatoes can go in as early as 2 weeks before it, from April 21 up to the median date[9]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after it, so May 19 is the earliest start[10]. These dates use the NOAA median last frost of May 5 as the average[6].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (May 5) is April 7 to April 21[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (May 5) is April 21, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, May 5[11]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (May 5), is May 19[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Apr 7 Jun 11 (from transplants)
Cabbage (hardy)[12] Apr 7 Jul 1 (from transplants)
Kohlrabi (hardy)[12] Apr 7 May 27
Lettuce (hardy)[12] Apr 7 Jun 6
Onions (hardy)[12] Apr 7 Jul 26
Peas (hardy)[12] Apr 7 Jun 11
Radishes (hardy)[12] Apr 7 May 7
Spinach (hardy)[12] Apr 7 May 17
Turnips (hardy)[12] Apr 7 May 27
Beets (semi-hardy)[12] Apr 21 Jun 20
Carrots (semi-hardy)[12] Apr 21 Jun 30
Cauliflower (semi-hardy)[12] Apr 21 not listed
Parsnips (semi-hardy)[12] Apr 21 Jun 30
Potatoes (semi-hardy)[12] Apr 21 Aug 24
Swiss chard (semi-hardy)[12] Apr 21 Jun 20
Snap beans (tender)[12] May 5 Jul 4
Sweet corn (tender)[12] May 5 Jul 4
Cucumbers (tender)[12] May 5 Jun 29
Summer squash (tender)[12] May 5 Jun 24
Cantaloupe (very tender)[12] May 19 Aug 12
Eggplant (very tender)[12] May 19 Jul 18 (from transplants)
Peppers (very tender)[12] May 19 Jul 28 (from transplants)
Tomatoes (very tender)[12] May 19 Jul 23 (from transplants)
Winter squash (very tender)[12] May 19 Aug 27
Watermelon (very tender)[12] May 19 Aug 12
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 zone number comes from the average coldest night of the winter, not from summer heat or frost dates[14]. Each half zone, a or b, covers 5°F[14]. The USDA map puts the center of Golden in zone 6a, but by land area 99% of the city lies in ZIP code areas rated zone 5b[1][15]. So parts of the city can differ[15].

Zone 6a: average annual extreme minimum temperature -10°F to -5°F (1991 to 2020)[1]. Modeled value at the city center: -8.2°F[1].

Share of the city's land area by ZIP code zone: zone 5b 99%[15].

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

Zone by ZIP code
ZIP code Zone Coldest night range
80401[15] 5b -15 to -10°F
80403[15] 5b -15 to -10°F
80465[15] 5b -15 to -10°F

Questions people ask

What growing zone is Golden, Colorado?
The center of Golden is in USDA zone 6a on the 2023 map[1]. By land area, 99% of the city lies in ZIP code areas rated zone 5b[15].
When is the last frost in Golden?
The median last spring frost is May 5, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 18[2].
When to plant tomatoes in Golden?
CSU Extension says tomatoes typically go in 2 or more weeks after the average last spring frost[10]. Using the median last frost, the earliest start is May 19[10].
When is the first frost in Golden?
The median first fall frost is October 5, so in half of years it comes before that date[3]. In 1 of 10 years it comes before September 20[3].
How long is the growing season in Golden?
In half of years the season between the last spring and first fall frost is at least 151 days[4]. In 9 of 10 years it is at least 132 days[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Golden, Colorado 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 8.2°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 24, in half of years after May 5, and in 1 of 10 years after May 18 (NOAA 1991 to 2020 normals). The median last frost date is May 5. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before September 20, in half of years before October 5, and in 9 of 10 years before October 18 (NOAA 1991 to 2020 normals). The median first frost date is October 5. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 132 days in 9 of 10 years, at least 151 days in half of years, and at least 167 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Wheat Ridge 2 weather station (USC00058995), 5.5 miles from the center of Golden at 5,398 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 25 and the median first fall date is October 14. 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. Golden, Colorado overlaps 3 ZIP code areas. By land area, 99% lies in ZIP code areas rated zone 5b. 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.