When to plant in Ontario, OR
USDA Zone 7aEverything below — frost dates, hardiness zone, and what to plant when in Ontario, Oregon — is derived from the closest NOAA station with complete climate normals.
Zone 7a means many perennials and even some tender shrubs overwinter in Ontario, while your frost dates still decide when annuals go out.
Frost probability
ONTARIO KSRV · 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 Ontario’s own odds, recorded at ONTARIO KSRV.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 21 | May 5 | Apr 21 | Sep 16 | Sep 30 | Oct 12 |
| 32°F | May 7 | Apr 22 | Apr 7 | Sep 26 | Oct 9 | Oct 23 |
| 28°F | Apr 23 | Apr 6 | Mar 18 | Oct 6 | Oct 21 | Nov 4 |
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 Ontario, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 6 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.
Ontario planting FAQ
When is the last spring frost in Ontario, OR?
On average, the last spring frost in Ontario is around April 22 (50% probability at 32°F, from 1991–2020 NOAA normals). Wait until after this date to set out tender plants like tomatoes and peppers.
When is the first fall frost in Ontario, OR?
Expect Ontario's first fall frost near October 9 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Ontario in?
Ontario is in USDA hardiness zone 7a. In zone 7a, winters are moderate — most common vegetables grow well in season.
How long is the growing season in Ontario?
There are roughly 170 frost-free days in Ontario (a moderate growing season), running from the average last frost around April 22 to the first fall frost near October 9.
When should I plant tomatoes in Ontario?
In Ontario, start tomato seeds indoors around February 25–March 11, then transplant seedlings outdoors around April 29 once the danger of frost has passed.
Never miss a window in Ontario
An email when it’s time to start seeds, transplant, and sow — timed to Ontario’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at ONTARIO KSRV, 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 Ontario, OR — Frost Dates & Zone 7a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00356294. Retrieved from https://blissgarden.com/oregon/ontario.