When to plant in Sioux City, IA
USDA Zone 5aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Sioux City, Iowa — all computed from Sioux City's nearest NOAA weather station.
Zone 5a means Sioux City sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
SIOUX CITY ANG · 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 Sioux City’s own odds, recorded at SIOUX CITY ANG.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 21 | May 7 | Apr 25 | Sep 18 | Sep 29 | Oct 11 |
| 32°F | May 11 | Apr 29 | Apr 15 | Sep 24 | Oct 7 | Oct 21 |
| 28°F | May 2 | Apr 19 | Apr 5 | Oct 2 | Oct 18 | Oct 30 |
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 Sioux City, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 38 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.
Sioux City planting FAQ
When is the last spring frost in Sioux City, IA?
Sioux City's average last spring frost falls near April 29 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Sioux City, IA?
In Sioux City, the first 32°F freeze of fall lands around October 7 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Sioux City in?
Sioux City is in USDA hardiness zone 5a. In zone 5a, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Sioux City?
There are roughly 161 frost-free days in Sioux City (a moderate growing season), running from the average last frost around April 29 to the first fall frost near October 7.
When should I plant tomatoes in Sioux City?
In Sioux City, start tomato seeds indoors around March 4–March 18, then transplant seedlings outdoors around May 6 once the danger of frost has passed.
Never miss a window in Sioux City
An email when it’s time to start seeds, transplant, and sow — timed to Sioux City’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- South Sioux City · 4 km
- Le Mars · 36 km
- Vermillion · 54 km
- Yankton · 93 km
- Storm Lake · 99 km
- Norfolk · 100 km
- Fremont · 118 km
- Sioux Falls · 120 km
Frost dates recorded at SIOUX CITY ANG, 11 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 Sioux City, IA — Frost Dates & Zone 5a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00137702. Retrieved from https://blissgarden.com/iowa/sioux-city.