When to plant in Ottawa, KS
USDA Zone 6bOttawa, Kansas frost dates, USDA zone, and a full-year planting calendar, drawn from the nearest NOAA station and tuned to the local season.
In zone 6b, Ottawa gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
Frost probability
OTTAWA · 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 Ottawa’s own odds, recorded at OTTAWA.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 10 | Apr 29 | Apr 15 | Sep 26 | Oct 9 | Oct 22 |
| 32°F | May 1 | Apr 18 | Apr 5 | Oct 3 | Oct 20 | Nov 1 |
| 28°F | Apr 22 | Apr 8 | Mar 24 | Oct 16 | Oct 30 | Nov 11 |
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 Ottawa, 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.
Ottawa planting FAQ
When is the last spring frost in Ottawa, KS?
Ottawa's average last spring frost falls near April 18 — 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 Ottawa, KS?
Expect Ottawa's first fall frost near October 20 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Ottawa in?
Ottawa is in USDA hardiness zone 6b. In zone 6b, winters are moderate — most common vegetables grow well in season.
How long is the growing season in Ottawa?
Ottawa has about 185 frost-free days — a moderate growing season — between the average last spring frost (April 18) and first fall frost (October 20).
When should I plant tomatoes in Ottawa?
For Ottawa, sow tomatoes indoors about February 21–March 7 and move the seedlings out around April 25, after the last spring frost.
Never miss a window in Ottawa
An email when it’s time to start seeds, transplant, and sow — timed to Ottawa’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at OTTAWA, 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 Ottawa, KS — Frost Dates & Zone 6b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00146128. Retrieved from https://blissgarden.com/kansas/ottawa.