Frost Dates & Planting Calendar for Alamosa, CO
Plan your garden around Alamosa, CO's typical frost-free growing season, using NOAA climate normals and a 42-crop planting calendar built for this location.
Last Spring Frost
May 30
Safe Jun 13
Typical May 30
Risky May 17
First Fall Frost
September 17
Safe Sep 4
Typical Sep 17
Risky Sep 27
Growing Season
108 days
Typical last frost to typical first frost.
USDA Hardiness Zone
Zone 4b
Very cold winters, focus on short-season varieties and cold-hardy perennials.
Data: NOAA station ALAMOSA 1E, CO US, 1.2 km away.
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days until the typical last spring frost
Monthly Temperatures
Avg. high
Avg. temp
Avg. low
Planting Calendar
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Tomato | Apr 4 – Apr 18 | — | Jun 6 – Jun 13 | — | 60–85 days | Start indoors 6-8 weeks before last frost; transplant out 1-2 weeks after last frost once soil has warmed. |
| Pepper | Mar 21 – Apr 4 | — | Jun 6 – Jun 20 | — | 60–90 days | Slow to germinate; start indoors 8-10 weeks before last frost. Transplant only once nights stay above 55F, 1-3 weeks after last frost. |
| Eggplant | Mar 21 – Apr 4 | — | Jun 13 – Jun 20 | — | 65–85 days | Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant. |
| Cucumber | May 2 – May 9 | Jun 6 – Jun 13 | Jun 6 – Jun 13 | — | 50–65 days | Can be started indoors 3-4 weeks before transplanting, or direct-sown 1-2 weeks after last frost once soil is warm. |
| Zucchini | May 9 – May 16 | Jun 6 – Jun 20 | Jun 6 – Jun 13 | — | 45–55 days | Fast-growing squash; direct sow 1-3 weeks after last frost, or start indoors 2-3 weeks early for a head start. |
| Winter Squash | May 2 – May 9 | Jun 6 – Jun 20 | Jun 6 – Jun 13 | — | 80–110 days | Long season; direct sow after soil warms, or start indoors 3-4 weeks before last frost in short-season climates. |
| Pumpkin | — | Jun 6 – Jun 20 | — | — | 90–120 days | Direct sow 1-3 weeks after last frost; back-time from your first fall frost so the 90-120 day maturity window lands before it. |
| Watermelon | May 2 – May 9 | — | Jun 13 – Jun 20 | — | 70–90 days | Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost. |
| Cantaloupe | May 2 – May 9 | — | Jun 13 – Jun 20 | — | 70–90 days | Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting. |
| Corn | — | May 30 – Jun 13 | — | — | 60–100 days | Direct sow at last frost to 2 weeks after, once soil reaches 60F; does not transplant well. Succession sow every 2 weeks. |
| Green Bean | — | May 30 – Jun 13 | — | — | 50–65 days | Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush. |
| Pea | — | Apr 18 – May 2 | — | — | 55–70 days | Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Lettuce | — | May 2 – May 16 | — | Jul 23 – Aug 6 | 45–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts. |
| Spinach | — | Apr 18 – May 2 | — | Jul 23 – Aug 6 | 40–50 days | Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Kale | — | May 2 – May 16 | — | Jul 9 – Jul 23 | 50–65 days | Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants. |
| Arugula | — | May 2 – May 16 | — | Aug 6 – Aug 13 | 30–40 days | Fast-growing, cold-tolerant green; direct sow 2-4 weeks before last frost, succession sow every 2-3 weeks. |
| Swiss Chard | — | May 9 – May 23 | — | — | 50–60 days | Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too. |
| Broccoli | Apr 11 – Apr 25 | — | May 9 – May 16 | Jul 16 – Jul 23 | 55–80 days | Start indoors 5-7 weeks before last frost; transplant out 2-3 weeks before last frost (hardens off to light frost). |
| Cauliflower | Apr 11 – Apr 25 | — | May 16 – May 23 | Jul 9 – Jul 16 | 55–85 days | Fussier than broccoli about temperature swings; start indoors 5-7 weeks before last frost, transplant 1-2 weeks before last frost. |
| Cabbage | Apr 11 – Apr 25 | — | May 2 – May 16 | Jul 9 – Jul 23 | 60–100 days | Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost. |
| Brussels Sprouts | Apr 11 – Apr 25 | — | May 9 – May 23 | — | 90–110 days | Long-season crop best timed to mature after a light fall frost for sweetest flavor; start indoors 5-7 weeks before last frost. |
| Carrot | — | May 2 – May 16 | — | Jun 25 – Jul 9 | 60–80 days | Direct sow only (does not transplant); sow 2-4 weeks before last frost, as soon as soil can be worked. |
| Beet | — | May 2 – May 16 | — | Jul 9 – Jul 23 | 50–65 days | Direct sow 2-4 weeks before last frost; tolerates light frost. |
| Radish | — | Apr 25 – May 9 | — | Aug 6 – Aug 20 | 22–30 days | Very fast and cold-hardy; direct sow 3-5 weeks before last frost, as soon as soil can be worked. |
| Turnip | — | May 2 – May 16 | — | Jul 9 – Jul 23 | 40–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. |
| Onion | Mar 21 – Apr 4 | — | May 2 – May 16 | — | 90–120 days | Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings. |
| Garlic | — | — | — | Aug 20 – Sep 3 | 240–270 days | Fall-planted crop only; not planted in spring in most climates. |
| Potato | — | May 2 – May 16 | — | — | 70–120 days | Plant seed potatoes 2-4 weeks before last frost, as soon as soil can be worked and is above 45F; light frost on emerging foliage is usually tolerated. |
| Sweet Potato | — | — | Jun 13 – Jun 27 | — | 90–120 days | Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive. |
| Asparagus | — | — | May 2 – May 16 | — | 730–1095 days | Perennial; plant crowns 2-4 weeks before last frost as soon as soil can be worked. Takes 2-3 years to full production. |
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Basil | Apr 18 – Apr 25 | — | Jun 6 – Jun 13 | — | 50–70 days | Very frost/cold sensitive; start indoors 5-6 weeks before last frost, transplant only after all danger of frost (1-2 weeks after) and nights stay warm. |
| Cilantro | — | May 9 – May 23 | — | Jul 23 – Aug 6 | 45–70 days | Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring. |
| Parsley | Apr 4 – Apr 18 | — | May 16 – May 23 | — | 70–90 days | Slow to germinate; start indoors 6-8 weeks before last frost, transplant 1-2 weeks before last frost (biennial, cold-tolerant). |
| Dill | — | May 9 – May 23 | — | — | 40–60 days | Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer. |
| Oregano | Apr 4 – Apr 18 | — | May 30 – Jun 6 | — | 80–90 days | Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date. |
| Thyme | Apr 4 – Apr 18 | — | May 30 – Jun 6 | — | 85–95 days | Perennial herb, slow from seed; start indoors 6-8 weeks before last frost, transplant around/after last frost. |
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Sunflower | — | Jun 6 – Jun 20 | — | — | 70–100 days | Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting. |
| Zinnia | May 2 – May 9 | Jun 6 – Jun 20 | Jun 6 – Jun 13 | — | 60–70 days | Frost-tender; direct sow 1-3 weeks after last frost, or start indoors 3-4 weeks early for earlier blooms. |
| Marigold | Apr 18 – May 2 | — | Jun 6 – Jun 13 | — | 45–60 days | Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed. |
| Cosmos | May 2 – May 9 | Jun 6 – Jun 20 | Jun 6 – Jun 13 | — | 60–90 days | Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early. |
| Nasturtium | — | Jun 6 – Jun 20 | — | — | 50–65 days | Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed. |
| Dahlia | — | — | Jun 6 – Jun 20 | — | 90–120 days | Plant tubers 1-3 weeks after last frost once soil is warm (60F+); very frost-sensitive. |
Date ranges are estimates based on university extension guidelines and this city's NOAA frost normals — not a guarantee. Scroll to see all columns on narrow screens.
Frequently Asked Questions
When is the last frost in Alamosa, CO?
Based on 1991–2020 NOAA climate normals for the ALAMOSA 1E, CO US station, the last spring frost in Alamosa typically falls around May 30. A cautious gardener might wait until June 13 (only a 10% chance of a later frost), while May 17 marks an earlier, higher-risk planting date.
When is the first frost in Alamosa, CO in fall?
The first fall frost in Alamosa typically arrives around September 17. To stay safe, assume frost could start as early as September 4; in milder years it can hold off until September 27.
How long is the growing season in Alamosa, CO?
Alamosa's average frost-free growing season is about 108 days, running from the typical last spring frost (May 30) to the typical first fall frost (September 17).
What USDA hardiness zone is Alamosa, CO in?
Alamosa, CO is in USDA plant hardiness zone 4b, per the USDA's 2023 Plant Hardiness Zone Map. Very cold winters, focus on short-season varieties and cold-hardy perennials.