Frost Dates & Planting Calendar for Rock Springs, WY
Plan your garden around Rock Springs, WY's typical frost-free growing season, using NOAA climate normals and a 42-crop planting calendar built for this location.
Last Spring Frost
May 24
Safe Jun 9
Typical May 24
Risky May 8
First Fall Frost
September 24
Safe Sep 9
Typical Sep 24
Risky Oct 4
Growing Season
121 days
Typical last frost to typical first frost.
USDA Hardiness Zone
Zone 5b
A classic four-season climate with cold winters and a solid summer growing season.
Data: NOAA station ROCK SPRINGS FIRE DEPT, WY US, 3.2 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 | Mar 29 – Apr 12 | — | May 31 – Jun 7 | — | 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 15 – Mar 29 | — | May 31 – Jun 14 | — | 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 15 – Mar 29 | — | Jun 7 – Jun 14 | — | 65–85 days | Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant. |
| Cucumber | Apr 26 – May 3 | May 31 – Jun 7 | May 31 – Jun 7 | — | 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 3 – May 10 | May 31 – Jun 14 | May 31 – Jun 7 | — | 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 | Apr 26 – May 3 | May 31 – Jun 14 | May 31 – Jun 7 | — | 80–110 days | Long season; direct sow after soil warms, or start indoors 3-4 weeks before last frost in short-season climates. |
| Pumpkin | — | May 31 – Jun 14 | — | — | 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 | Apr 26 – May 3 | — | Jun 7 – Jun 14 | — | 70–90 days | Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost. |
| Cantaloupe | Apr 26 – May 3 | — | Jun 7 – Jun 14 | — | 70–90 days | Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting. |
| Corn | — | May 24 – Jun 7 | — | — | 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 24 – Jun 7 | — | — | 50–65 days | Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush. |
| Pea | — | Apr 12 – Apr 26 | — | — | 55–70 days | Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Lettuce | — | Apr 26 – May 10 | — | Jul 30 – Aug 13 | 45–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts. |
| Spinach | — | Apr 12 – Apr 26 | — | Jul 30 – Aug 13 | 40–50 days | Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Kale | — | Apr 26 – May 10 | — | Jul 16 – Jul 30 | 50–65 days | Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants. |
| Arugula | — | Apr 26 – May 10 | — | Aug 13 – Aug 20 | 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 3 – May 17 | — | — | 50–60 days | Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too. |
| Broccoli | Apr 5 – Apr 19 | — | May 3 – May 10 | Jul 23 – Jul 30 | 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 5 – Apr 19 | — | May 10 – May 17 | Jul 16 – Jul 23 | 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 5 – Apr 19 | — | Apr 26 – May 10 | Jul 16 – Jul 30 | 60–100 days | Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost. |
| Brussels Sprouts | Apr 5 – Apr 19 | — | May 3 – May 17 | — | 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 | — | Apr 26 – May 10 | — | Jul 2 – Jul 16 | 60–80 days | Direct sow only (does not transplant); sow 2-4 weeks before last frost, as soon as soil can be worked. |
| Beet | — | Apr 26 – May 10 | — | Jul 16 – Jul 30 | 50–65 days | Direct sow 2-4 weeks before last frost; tolerates light frost. |
| Radish | — | Apr 19 – May 3 | — | Aug 13 – Aug 27 | 22–30 days | Very fast and cold-hardy; direct sow 3-5 weeks before last frost, as soon as soil can be worked. |
| Turnip | — | Apr 26 – May 10 | — | Jul 16 – Jul 30 | 40–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. |
| Onion | Mar 15 – Mar 29 | — | Apr 26 – May 10 | — | 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 27 – Sep 10 | 240–270 days | Fall-planted crop only; not planted in spring in most climates. |
| Potato | — | Apr 26 – May 10 | — | — | 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 7 – Jun 21 | — | 90–120 days | Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive. |
| Asparagus | — | — | Apr 26 – May 10 | — | 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 12 – Apr 19 | — | May 31 – Jun 7 | — | 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 3 – May 17 | — | Jul 30 – Aug 13 | 45–70 days | Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring. |
| Parsley | Mar 29 – Apr 12 | — | May 10 – May 17 | — | 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 3 – May 17 | — | — | 40–60 days | Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer. |
| Oregano | Mar 29 – Apr 12 | — | May 24 – May 31 | — | 80–90 days | Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date. |
| Thyme | Mar 29 – Apr 12 | — | May 24 – May 31 | — | 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 | — | May 31 – Jun 14 | — | — | 70–100 days | Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting. |
| Zinnia | Apr 26 – May 3 | May 31 – Jun 14 | May 31 – Jun 7 | — | 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 12 – Apr 26 | — | May 31 – Jun 7 | — | 45–60 days | Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed. |
| Cosmos | Apr 26 – May 3 | May 31 – Jun 14 | May 31 – Jun 7 | — | 60–90 days | Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early. |
| Nasturtium | — | May 31 – Jun 14 | — | — | 50–65 days | Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed. |
| Dahlia | — | — | May 31 – Jun 14 | — | 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 Rock Springs, WY?
Based on 1991–2020 NOAA climate normals for the ROCK SPRINGS FIRE DEPT, WY US station, the last spring frost in Rock Springs typically falls around May 24. A cautious gardener might wait until June 9 (only a 10% chance of a later frost), while May 8 marks an earlier, higher-risk planting date.
When is the first frost in Rock Springs, WY in fall?
The first fall frost in Rock Springs typically arrives around September 24. To stay safe, assume frost could start as early as September 9; in milder years it can hold off until October 4.
How long is the growing season in Rock Springs, WY?
Rock Springs's average frost-free growing season is about 121 days, running from the typical last spring frost (May 24) to the typical first fall frost (September 24).
What USDA hardiness zone is Rock Springs, WY in?
Rock Springs, WY is in USDA plant hardiness zone 5b, per the USDA's 2023 Plant Hardiness Zone Map. A classic four-season climate with cold winters and a solid summer growing season.