Frost dates for 51103Sioux City, IA
The average last spring frost in Sioux City is April 29 and the average first fall frost is October 5, giving a typical growing season of about 159 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 29
- Average first fall frost
- Oct 5
- Growing season
- 159 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 22 (1-in-10 risk)
Last frost typically in 184 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) | Apr 26 · May 7 · May 21 | Sep 14 · Sep 28 · Oct 9 | 142 days | 100% |
| Frost / freeze (32°F) | Apr 16 · Apr 29 · May 14 | Sep 22 · Oct 5 · Oct 18 | 159 days | 100% |
| Hard freeze (28°F) | Apr 7 · Apr 20 · May 3 | Sep 29 · Oct 15 · Oct 28 | 177 days | 100% |
Planting calendar for Sioux City
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 | Mar 29 – Jun 4 |
| Tomatoes | Transplant outdoors | May 15 – Jun 15 |
| Peppers | Start seeds indoors | Mar 29 – Apr 29 |
| Peppers | Transplant outdoors | May 29 – Jun 29 |
| Eggplant | Start seeds indoors | Apr 15 – May 14 |
| Eggplant | Transplant outdoors | May 29 – Jun 29 |
| Cucumbers | Sow outdoors | May 29 – Jun 25 |
| Summer squash | Sow outdoors | May 15 – Jun 29 |
| Winter squash & pumpkins | Sow outdoors | May 29 – Jun 29 |
| Snap beans | Sow outdoors | May 15 – Jul 18 |
| Sweet corn | Sow outdoors | May 15 – Jun 15 |
| Watermelon & cantaloupe | Sow outdoors | May 29 – Jun 29 |
| Okra | Sow outdoors | May 22 – Jun 14 |
| Peas | Sow outdoors (spring) | Mar 29 – May 14 |
| Potatoes | Plant outdoors (spring) | Mar 29 – May 29 |
| Onions | Start seeds indoors (spring) | Feb 15 – Mar 14 |
| Onions | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (spring) | Mar 11 – Apr 14 |
| Broccoli | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (fall) | Jun 5 – Jun 15 |
| Broccoli | Transplant outdoors (fall) | Jul 5 – Jul 16 |
| Cabbage | Start seeds indoors (spring) | Mar 1 – Mar 29 |
| Cabbage | Transplant outdoors (spring) | Mar 29 – Apr 29 |
| Cabbage | Start seeds indoors (fall) | May 26 – Jun 25 |
| Cabbage | Transplant outdoors (fall) | Jun 25 – Jul 26 |
| Leaf lettuce | Sow outdoors (spring) | Mar 29 – Jun 14 |
| Leaf lettuce | Sow outdoors (fall) | Jun 25 – Aug 11 |
| Spinach | Sow outdoors (spring) | Mar 22 – May 5 |
| Spinach | Sow outdoors (fall) | Jul 12 – Aug 16 |
| Radishes | Sow outdoors (spring) | Mar 29 – May 19 |
| Radishes | Sow outdoors (fall) | Jun 25 – Aug 26 |
| Kale | Sow outdoors (spring) | Apr 15 – May 5 |
| Kale | Sow outdoors (fall) | Jun 18 – Jul 26 |
| Carrots | Sow outdoors (spring) | Apr 29 – Jun 14 |
| Carrots | Sow outdoors (fall) | May 26 – Jul 11 |
| Garlic | Plant outdoors (fall) | Sep 25 – Oct 26 |
Where these dates come from
ZIP code 51103 is matched to the NOAA station Sioux City Gateway Ap, IA, 13.5 km away, at 1,095 ft elevation (66 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Sioux City Gateway Ap, IA (used) | 1,095 ft | Apr 29 | Oct 5 |
| Sioux City Ang, IA | 1,100 ft | Apr 29 | Oct 7 |
| Le Mars, IA | 1,195 ft | Apr 30 | Oct 4 |
| Walthill 1E, NE | 1,280 ft | May 1 | Oct 6 |
Frost dates near Sioux City
- Sioux City, IA 51101 · last Apr 29, first Oct 5
- South Sioux City, NE 68776 · last Apr 29, first Oct 5
- North Sioux City, SD 57049 · last Apr 29, first Oct 5
- Sergeant Bluff, IA 51054 · last Apr 29, first Oct 5
- Jackson, NE 68743 · last Apr 29, first Oct 5
- Dakota City, NE 68731 · last Apr 29, first Oct 5
- Hinton, IA 51024 · last Apr 30, first Oct 4
- Jefferson, SD 57038 · last Apr 29, first Oct 5
Frequently asked questions
- When is the last frost in Sioux City, IA?
- For ZIP code 51103, the average last spring frost (32°F) is April 29, based on NOAA 1991-2020 climate normals for the Sioux City Gateway Ap, IA weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Sioux City, IA?
- The average first fall frost (32°F) is October 5. There is a 1-in-10 chance of frost by September 22, so tender plants are at risk from that point on.
- How long is the growing season in 51103?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 159 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.