Frost dates for 57201Watertown, SD
The average last spring frost in Watertown is May 7 and the average first fall frost is September 30, giving a typical growing season of about 145 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 7
- Average first fall frost
- Sep 30
- Growing season
- 145 days
Safer after May 20 (1-in-10 risk)
Possible by Sep 19 (1-in-10 risk)
Last frost typically in 192 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 4 · May 17 · May 31 | Sep 9 · Sep 23 · Oct 4 | 127 days | 100% |
| Frost / freeze (32°F) | Apr 26 · May 7 · May 20 | Sep 19 · Sep 30 · Oct 13 | 145 days | 100% |
| Hard freeze (28°F) | Apr 14 · Apr 29 · May 11 | Sep 26 · Oct 9 · Oct 22 | 164 days | 100% |
Planting calendar for Watertown
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 6 – Jun 12 |
| Tomatoes | Transplant outdoors | May 23 – Jun 10 |
| Peppers | Start seeds indoors | Apr 6 – May 7 |
| Peppers | Transplant outdoors | Jun 6 – Jul 7 |
| Eggplant | Start seeds indoors | Apr 23 – May 22 |
| Eggplant | Transplant outdoors | Jun 6 – Jul 7 |
| Cucumbers | Sow outdoors | Jun 6 – Jun 20 |
| Summer squash | Sow outdoors | May 23 – Jul 7 |
| Winter squash & pumpkins | Sow outdoors | Jun 6 – Jul 7 |
| Snap beans | Sow outdoors | May 23 – Jul 13 |
| Sweet corn | Sow outdoors | May 23 – Jun 10 |
| Watermelon & cantaloupe | Sow outdoors | Jun 6 – Jul 7 |
| Okra | Sow outdoors | May 30 – Jun 22 |
| Peas | Sow outdoors (spring) | Apr 6 – May 22 |
| Potatoes | Plant outdoors (spring) | Apr 6 – Jun 6 |
| Onions | Start seeds indoors (spring) | Feb 23 – Mar 22 |
| Onions | Transplant outdoors (spring) | Apr 23 – May 22 |
| Broccoli | Start seeds indoors (spring) | Mar 19 – Apr 22 |
| Broccoli | Transplant outdoors (spring) | Apr 23 – May 22 |
| Broccoli | Start seeds indoors (fall) | May 31 – Jun 10 |
| Broccoli | Transplant outdoors (fall) | Jun 30 – Jul 11 |
| Cabbage | Start seeds indoors (spring) | Mar 9 – Apr 6 |
| Cabbage | Transplant outdoors (spring) | Apr 6 – May 7 |
| Cabbage | Start seeds indoors (fall) | May 21 – Jun 20 |
| Cabbage | Transplant outdoors (fall) | Jun 20 – Jul 21 |
| Leaf lettuce | Sow outdoors (spring) | Apr 6 – Jun 22 |
| Leaf lettuce | Sow outdoors (fall) | Jun 20 – Aug 6 |
| Spinach | Sow outdoors (spring) | Mar 30 – May 13 |
| Spinach | Sow outdoors (fall) | Jul 7 – Aug 11 |
| Radishes | Sow outdoors (spring) | Apr 6 – May 27 |
| Radishes | Sow outdoors (fall) | Jun 20 – Aug 21 |
| Kale | Sow outdoors (spring) | Apr 23 – May 13 |
| Kale | Sow outdoors (fall) | Jun 13 – Jul 21 |
| Carrots | Sow outdoors (spring) | May 7 – Jun 22 |
| Carrots | Sow outdoors (fall) | May 21 – Jul 6 |
| Garlic | Plant outdoors (fall) | Sep 20 – Oct 21 |
Where these dates come from
ZIP code 57201 is matched to the NOAA station Watertown Rgnl Ap, SD, 2 km away, at 1,748 ft elevation (26 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Watertown Rgnl Ap, SD (used) | 1,748 ft | May 7 | Sep 30 |
| Watertown 2 S, SD | 1,772 ft | May 3 | Oct 4 |
| Rauville 2 W, SD | 1,737 ft | May 7 | Sep 28 |
| Castlewood #2, SD | 1,689 ft | May 6 | Oct 1 |
Frost dates near Watertown
- Kranzburg, SD 57245 · last May 7, first Sep 30
- Castlewood, SD 57223 · last May 10, first Sep 27
- Goodwin, SD 57238 · last May 7, first Oct 1
- Florence, SD 57235 · last May 7, first Sep 30
- Hazel, SD 57242 · last May 7, first Sep 30
- South Shore, SD 57263 · last May 14, first Sep 28
- Henry, SD 57243 · last May 5, first Oct 5
- Hayti, SD 57241 · last May 10, first Sep 27
Frequently asked questions
- When is the last frost in Watertown, SD?
- For ZIP code 57201, the average last spring frost (32°F) is May 7, based on NOAA 1991-2020 climate normals for the Watertown Rgnl Ap, SD weather station. There is a 1-in-10 chance of a frost after May 20.
- When is the first frost in Watertown, SD?
- The average first fall frost (32°F) is September 30. There is a 1-in-10 chance of frost by September 19, so tender plants are at risk from that point on.
- How long is the growing season in 57201?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 145 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.