Frost Dates & Planting Calendar for Watertown, SD
Plan your garden around Watertown, SD's typical frost-free growing season, using NOAA climate normals and a 42-crop planting calendar built for this location.
Last Spring Frost
May 7
Safe May 20
Typical May 7
Risky Apr 26
First Fall Frost
September 30
Safe Sep 19
Typical Sep 30
Risky Oct 13
Growing Season
145 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 WATERTOWN RGNL AP, SD US, 2.8 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 12 – Mar 26 | — | May 14 – May 21 | — | 60–85 days | Start indoors 6-8 weeks before last frost; transplant out 1-2 weeks after last frost once soil has warmed. |
| Pepper | Feb 26 – Mar 12 | — | May 14 – May 28 | — | 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 | Feb 26 – Mar 12 | — | May 21 – May 28 | — | 65–85 days | Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant. |
| Cucumber | Apr 9 – Apr 16 | May 14 – May 21 | May 14 – May 21 | — | 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 | Apr 16 – Apr 23 | May 14 – May 28 | May 14 – May 21 | — | 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 9 – Apr 16 | May 14 – May 28 | May 14 – May 21 | — | 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 14 – May 28 | — | — | 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 9 – Apr 16 | — | May 21 – May 28 | — | 70–90 days | Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost. |
| Cantaloupe | Apr 9 – Apr 16 | — | May 21 – May 28 | — | 70–90 days | Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting. |
| Corn | — | May 7 – May 21 | — | — | 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 7 – May 21 | — | — | 50–65 days | Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush. |
| Pea | — | Mar 26 – Apr 9 | — | — | 55–70 days | Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Lettuce | — | Apr 9 – Apr 23 | — | Aug 5 – Aug 19 | 45–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts. |
| Spinach | — | Mar 26 – Apr 9 | — | Aug 5 – Aug 19 | 40–50 days | Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Kale | — | Apr 9 – Apr 23 | — | Jul 22 – Aug 5 | 50–65 days | Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants. |
| Arugula | — | Apr 9 – Apr 23 | — | Aug 19 – Aug 26 | 30–40 days | Fast-growing, cold-tolerant green; direct sow 2-4 weeks before last frost, succession sow every 2-3 weeks. |
| Swiss Chard | — | Apr 16 – Apr 30 | — | — | 50–60 days | Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too. |
| Broccoli | Mar 19 – Apr 2 | — | Apr 16 – Apr 23 | Jul 29 – Aug 5 | 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 | Mar 19 – Apr 2 | — | Apr 23 – Apr 30 | Jul 22 – Jul 29 | 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 | Mar 19 – Apr 2 | — | Apr 9 – Apr 23 | Jul 22 – Aug 5 | 60–100 days | Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost. |
| Brussels Sprouts | Mar 19 – Apr 2 | — | Apr 16 – Apr 30 | — | 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 9 – Apr 23 | — | Jul 8 – Jul 22 | 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 9 – Apr 23 | — | Jul 22 – Aug 5 | 50–65 days | Direct sow 2-4 weeks before last frost; tolerates light frost. |
| Radish | — | Apr 2 – Apr 16 | — | Aug 19 – Sep 2 | 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 9 – Apr 23 | — | Jul 22 – Aug 5 | 40–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. |
| Onion | Feb 26 – Mar 12 | — | Apr 9 – Apr 23 | — | 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 | — | — | — | Sep 2 – Sep 16 | 240–270 days | Fall-planted crop only; not planted in spring in most climates. |
| Potato | — | Apr 9 – Apr 23 | — | — | 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 | — | — | May 21 – Jun 4 | — | 90–120 days | Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive. |
| Asparagus | — | — | Apr 9 – Apr 23 | — | 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 | Mar 26 – Apr 2 | — | May 14 – May 21 | — | 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 | — | Apr 16 – Apr 30 | — | Aug 5 – Aug 19 | 45–70 days | Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring. |
| Parsley | Mar 12 – Mar 26 | — | Apr 23 – Apr 30 | — | 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 | — | Apr 16 – Apr 30 | — | — | 40–60 days | Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer. |
| Oregano | Mar 12 – Mar 26 | — | May 7 – May 14 | — | 80–90 days | Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date. |
| Thyme | Mar 12 – Mar 26 | — | May 7 – May 14 | — | 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 14 – May 28 | — | — | 70–100 days | Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting. |
| Zinnia | Apr 9 – Apr 16 | May 14 – May 28 | May 14 – May 21 | — | 60–70 days | Frost-tender; direct sow 1-3 weeks after last frost, or start indoors 3-4 weeks early for earlier blooms. |
| Marigold | Mar 26 – Apr 9 | — | May 14 – May 21 | — | 45–60 days | Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed. |
| Cosmos | Apr 9 – Apr 16 | May 14 – May 28 | May 14 – May 21 | — | 60–90 days | Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early. |
| Nasturtium | — | May 14 – May 28 | — | — | 50–65 days | Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed. |
| Dahlia | — | — | May 14 – May 28 | — | 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 Watertown, SD?
Based on 1991–2020 NOAA climate normals for the WATERTOWN RGNL AP, SD US station, the last spring frost in Watertown typically falls around May 7. A cautious gardener might wait until May 20 (only a 10% chance of a later frost), while April 26 marks an earlier, higher-risk planting date.
When is the first frost in Watertown, SD in fall?
The first fall frost in Watertown typically arrives around September 30. To stay safe, assume frost could start as early as September 19; in milder years it can hold off until October 13.
How long is the growing season in Watertown, SD?
Watertown's average frost-free growing season is about 145 days, running from the typical last spring frost (May 7) to the typical first fall frost (September 30).
What USDA hardiness zone is Watertown, SD in?
Watertown, SD 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.