Eldora, CO planting calendar
- USDA zone
- 5b−15 to −10 °F
- Last frost
- Jun 21avg, 32°F
- First frost
- Sep 2avg, 32°F
- Growing season
- 71days
Eldora, Colorado is in USDA plant hardiness zone 5b. Its average last spring frost is around June 21 and the first fall frost around September 2, giving a growing season of about 71 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Eldora planting calendar
Each crop's windows are counted from Eldora's average frost dates. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Apr 26 – May 10 | Jun 28 – Jul 5 | Aug 27 – Sep 16 | — |
| Pepper | Very tender | Apr 12 – Apr 26 | Jul 5 – Jul 12 | Sep 3 – Oct 3 | — |
| Cucumber | Tender | May 24 – May 31 | Jun 28 – Jul 5 | Aug 17 – Sep 6 | — |
| Summer squash / zucchini | Tender | — | Jun 28 – Jul 5 | Aug 12 – Aug 27 | — |
| Bush bean | Tender | — | Jun 28 – Jul 5 | Aug 17 – Aug 27 | Jul 4 – Jul 14 |
| Sweet corn | Tender | — | Jun 21 – Jul 5 | Aug 20 – Sep 19 | — |
| Basil | Very tender | May 10 – May 24 | Jun 28 – Jul 5 | Jul 28 – Aug 12 | — |
| Lettuce | Half-hardy | May 10 – May 24 | May 24 – Jun 7 | Jul 8 – Jul 23 | Jun 20 – Jul 5 |
| Pea | Hardy | — | May 10 – May 24 | Jul 4 – Jul 19 | Jun 10 – Jun 25 |
| Spinach | Hardy | — | May 10 – May 24 | Jun 19 – Jun 29 | Jun 30 – Jul 10 |
| Carrot | Half-hardy | — | May 31 – Jun 7 | Jul 30 – Aug 19 | May 31 – Jun 20 |
| Broccoli | Half-hardy | Apr 26 – May 10 | May 24 – Jun 7 | Jul 18 – Aug 7 | Jun 5 – Jun 25 |
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USW00094075. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 (p10 for spring, p90 for fall) — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | — | — | — | — | 39 |
| 32°F (freeze) | Jun 21 | Jul 4 | Sep 2 | Sep 15 | 71 |
| 28°F | Jun 4 | Jun 20 | Sep 14 | Sep 27 | 100 |
| 24°F | May 19 | Jun 4 | Sep 25 | Oct 9 | 126 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 385 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 1,526 | cool-season crops (brassicas, greens) |
Hardiness zone 5b
Eldora sits in USDA plant hardiness zone 5b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −15 to −10 °F. That number tells you which perennials, shrubs, and trees reliably survive an average winter here; it does not set your planting dates, which come from the frost calendar above.
Explore more places in zone 5b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Eldora?
- Eldora, Colorado is in USDA plant hardiness zone 5b on the 2023 map (average annual extreme minimum temperature −15 to −10 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Eldora?
- The average (median) last spring frost at 32°F is around June 21, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as July 4, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Eldora?
- The average first fall frost at 32°F is around September 2. That leaves a growing season of about 71 days between the average last spring and first fall frosts.
- When should I start tomatoes in Eldora?
- Start tomato seeds indoors about Apr 26 – May 10 and transplant them outside about Jun 28 – Jul 5, once the danger of frost has passed. Estimated first harvest is around Aug 27 – Sep 16.
- How long is the growing season in Eldora?
- About 71 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~June 21) and the average first fall frost (~September 2). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USW00094075 (Boulder 14 W, 5.3 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.