Frost dates · USDA zone 5a
Frost dates for Sioux City, IA
Sioux City, IA sees its last 32 °F night of spring around April 29 and its first of fall around October 7 — a 161-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Apr 15 | Oct 21 |
| Median — 1 year in 2 | Apr 29 | Oct 7 |
| 1 year in 10 | May 11 | Sep 24 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 161 days median, at least 143 in 9 years of 10, at least 178 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Apr 19 and first of Oct 18.
Sioux City planting calendar, 2027
Every row runs from the median last frost (Apr 29) and median first frost (Oct 7) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Feb 4 | Apr 1 | Jul 20 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | Apr 29 | May 29 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 15 | Apr 15 | May 30 | 45 from sow |
| Genovese BasilGenovese | Apr 1 | May 13 | Jul 12 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Mar 4 | May 6 | Jul 20 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Feb 18 | May 13 | Aug 16 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Mar 4 | May 6 | Jul 20 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Mar 4 | May 6 | Jul 25 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Mar 4 | May 6 | Jul 25 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 15 | Apr 15 | Jun 24 | 70 from sow |
| TomatilloToma Verde | Mar 18 | May 6 | Jul 15 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 18 | May 6 | Jul 20 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 18 | May 6 | Jul 25 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Sioux City grow?
Each sauce, scheduled for a Sioux City container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Sioux City frost questions
When is the last frost in Sioux City, IA?
The median last 32 °F freeze at SIOUX CITY ANG, IA is April 29: half of years see a later one. One year in ten, a freeze still comes after May 11; nine years in ten, it comes after April 15. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Sioux City, IA?
The median first 32 °F freeze of fall is October 7. One year in ten it arrives before September 24; nine years in ten, before October 21.
How long is the growing season in Sioux City, IA?
161 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 143 days; one year in ten, at least 178 days.
What growing zone is Sioux City, IA?
USDA hardiness zone 5a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 51101. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Sioux City, IA?
Start Roma VF (determinate paste) seeds indoors around Mar 18 and transplant around May 6, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 11. First ripe fruit lands around Jul 20.
When should I plant peppers in Sioux City, IA?
Sow jalapeño indoors on a heat mat around Mar 4; transplant no earlier than May 6, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 20.
Nearby in Iowa
- Council Bluffslast frost Apr 18
- Ameslast frost Apr 26
- Urbandalelast frost Apr 18
- West Des Moineslast frost Apr 18
- Ankenylast frost Apr 23
- Des Moineslast frost Apr 18
All Iowa frost dates → · How frost-date math drives a sowing calendar →