When to plant in Oskaloosa, IA
USDA Zone 5bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Oskaloosa, Iowa — all computed from Oskaloosa's nearest NOAA weather station.
In zone 5b, Oskaloosa gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
The average first fall frost in Oskaloosa is now 8 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
OSKALOOSA · 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 Oskaloosa’s own odds, recorded at OSKALOOSA.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 14 | May 1 | Apr 18 | Sep 21 | Oct 4 | Oct 19 |
| 32°F | May 4 | Apr 21 | Apr 8 | Sep 29 | Oct 16 | Oct 29 |
| 28°F | Apr 26 | Apr 11 | Mar 29 | Oct 10 | Oct 27 | Nov 8 |
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 Oskaloosa, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 28 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.
Oskaloosa planting FAQ
When is the last spring frost in Oskaloosa, IA?
Oskaloosa's average last spring frost falls near April 21 — 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 Oskaloosa, IA?
The first fall frost in Oskaloosa typically arrives around October 16 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Oskaloosa in?
Oskaloosa is in USDA hardiness zone 5b. In zone 5b, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Oskaloosa?
Oskaloosa has about 178 frost-free days — a moderate growing season — between the average last spring frost (April 21) and first fall frost (October 16).
When should I plant tomatoes in Oskaloosa?
For Oskaloosa, sow tomatoes indoors about February 24–March 10 and move the seedlings out around April 28, after the last spring frost.
Never miss a window in Oskaloosa
An email when it’s time to start seeds, transplant, and sow — timed to Oskaloosa’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Pella · 26 km
- Ottumwa · 35 km
- Newton · 56 km
- Indianola · 78 km
- Pleasant Hill · 80 km
- Altoona · 80 km
- Marshalltown · 85 km
- Des Moines · 87 km
Frost dates recorded at OSKALOOSA, 3 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 Oskaloosa, IA — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00136327. Retrieved from https://blissgarden.com/iowa/oskaloosa.