When to plant in Watertown, SD
USDA Zone 4bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Watertown, South Dakota — all computed from Watertown's nearest NOAA weather station.
In zone 4b, Watertown winters are severe; choose cold-hardy perennials and time annuals carefully around the frost dates above.
Frost probability
WATERTOWN RGNL AP · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Watertown’s own odds, recorded at WATERTOWN RGNL AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 31 | May 17 | May 4 | Sep 9 | Sep 23 | Oct 4 |
| 32°F | May 20 | May 7 | Apr 26 | Sep 19 | Sep 30 | Oct 13 |
| 28°F | May 11 | Apr 29 | Apr 14 | Sep 26 | Oct 9 | Oct 22 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Watertown, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 7 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Watertown planting FAQ
When is the last spring frost in Watertown, SD?
Plan for the last spring frost in Watertown around May 7 (the date it has a 50% chance of a 32°F freeze). Anything frost-sensitive should go out after it.
When is the first fall frost in Watertown, SD?
Expect Watertown's first fall frost near September 30 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Watertown in?
Watertown is in USDA hardiness zone 4b. In zone 4b, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Watertown?
Watertown has about 146 frost-free days — a short growing season — between the average last spring frost (May 7) and first fall frost (September 30).
When should I plant tomatoes in Watertown?
For Watertown, sow tomatoes indoors about March 12–March 26 and move the seedlings out around May 14, after the last spring frost.
Never miss a window in Watertown
An email when it’s time to start seeds, transplant, and sow — timed to Watertown’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at WATERTOWN RGNL AP, 1 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Watertown, SD — Frost Dates & Zone 4b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00014946. Retrieved from https://blissgarden.com/south-dakota/watertown.