When to plant in Spencer, IA
USDA Zone 5aEverything below — frost dates, hardiness zone, and what to plant when in Spencer, Iowa — is derived from the closest NOAA station with complete climate normals.
Zone 5a means Spencer sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
SPENCER 1 N · 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 Spencer’s own odds, recorded at SPENCER 1 N.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 23 | May 10 | Apr 29 | Sep 11 | Sep 24 | Oct 7 |
| 32°F | May 14 | May 1 | Apr 18 | Sep 20 | Oct 3 | Oct 17 |
| 28°F | May 5 | Apr 22 | Apr 8 | Sep 28 | Oct 14 | Oct 27 |
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 Spencer, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 26 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.
Spencer planting FAQ
When is the last spring frost in Spencer, IA?
Plan for the last spring frost in Spencer around May 1 (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 Spencer, IA?
Expect Spencer's first fall frost near October 3 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Spencer in?
Spencer 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 Spencer?
There are roughly 155 frost-free days in Spencer (a moderate growing season), running from the average last frost around May 1 to the first fall frost near October 3.
When should I plant tomatoes in Spencer?
In Spencer, start tomato seeds indoors around March 6–March 20, then transplant seedlings outdoors around May 8 once the danger of frost has passed.
Never miss a window in Spencer
An email when it’s time to start seeds, transplant, and sow — timed to Spencer’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Storm Lake · 56 km
- Worthington · 65 km
- Fairmont · 78 km
- Le Mars · 92 km
- Fort Dodge · 107 km
- Carroll · 122 km
- Sioux City · 124 km
- Brandon · 126 km
Frost dates recorded at SPENCER 1 N, 2 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 Spencer, IA — Frost Dates & Zone 5a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00137844. Retrieved from https://blissgarden.com/iowa/spencer.