Spencer, IA planting zone & frost dates
Spencer is in USDA hardiness zone 5a. The last spring frost usually comes around May 1 and the first fall frost around October 3, for a growing season of about 154 days.
Planting calendar for Spencer
Dates are counted from the average last spring frost (May 1) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 6 – Mar 20 Transplant outdoors: May 8 – May 15 |
| Peppers | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: May 15 – May 22 |
| Eggplant | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: May 15 – May 22 |
| Broccoli | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: Apr 3 – Apr 17 |
| Cabbage | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: Apr 3 – Apr 17 |
| Onions (sets) | Plant outdoors: Apr 3 – Apr 17 |
| Peas | Sow outdoors: Mar 20 – Apr 3 |
| Spinach | Sow outdoors: Mar 20 – Apr 3 |
| Lettuce | Sow outdoors: Apr 3 – Apr 17 |
| Carrots | Sow outdoors: Apr 3 – Apr 17 |
| Potatoes | Plant outdoors: Apr 3 – Apr 17 |
| Beans | Sow outdoors: May 8 – May 15 |
| Sweet corn | Sow outdoors: May 8 – May 15 |
| Cucumbers | Sow outdoors: May 8 – May 15 |
| Squash & zucchini | Sow outdoors: May 8 – May 15 |
| Basil | Start seeds indoors: Mar 20 – Apr 3 Transplant outdoors: May 8 – May 15 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 8 (8 weeks before the average first fall frost on Oct 3).
Useful for zone 5a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 18 | May 1 | May 14 |
| First 32°F frost in fall is before | Oct 17 | Oct 3 | Sep 20 |
How to read it: in spring there is a 10% chance of a frost after May 14, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 20. A hard freeze (28°F) usually ends around April 22.
Hardiness zone by ZIP code in Spencer
- 51301 zone 5a
Nearby cities
- Storm Lake zone 5a, last frost Apr 25
- Fort Dodge zone 5a, last frost Apr 28
- Sioux City zone 5a, last frost Apr 29
- Boone zone 5a, last frost Apr 28
- Ames zone 5b, last frost Apr 26
- Mason City zone 5a, last frost Apr 29
- Waukee zone 5b, last frost Apr 19
- Grimes zone 5b, last frost Apr 19
Questions
What growing zone is Spencer, IA?
Spencer is in USDA Plant Hardiness Zone 5a (average extreme winter low -20°F to -15°F), according to the USDA 2023 map.
When is the last frost in Spencer?
The average last spring frost (32°F) in Spencer is May 1. There is still a 10% chance of frost until May 14.
When can I plant tomatoes in Spencer?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 8 – May 15. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Spencer 1 N, IA (USC00137844), 2.7 km (1.7 mi) from the city center, elevation 404 m, based on 29 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.