Ontario, OR planting zone & frost dates
Ontario is in USDA hardiness zone 7a. The last spring frost usually comes around April 22 and the first fall frost around October 9, for a growing season of about 168 days.
Planting calendar for Ontario
Dates are counted from the average last spring frost (April 22) 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: Feb 25 – Mar 11 Transplant outdoors: Apr 29 – May 6 |
| Peppers | Start seeds indoors: Feb 11 – Feb 25 Transplant outdoors: May 6 – May 13 |
| Eggplant | Start seeds indoors: Feb 11 – Feb 25 Transplant outdoors: May 6 – May 13 |
| Broccoli | Start seeds indoors: Feb 11 – Feb 25 Transplant outdoors: Mar 25 – Apr 8 |
| Cabbage | Start seeds indoors: Feb 11 – Feb 25 Transplant outdoors: Mar 25 – Apr 8 |
| Onions (sets) | Plant outdoors: Mar 25 – Apr 8 |
| Peas | Sow outdoors: Mar 11 – Mar 25 |
| Spinach | Sow outdoors: Mar 11 – Mar 25 |
| Lettuce | Sow outdoors: Mar 25 – Apr 8 |
| Carrots | Sow outdoors: Mar 25 – Apr 8 |
| Potatoes | Plant outdoors: Mar 25 – Apr 8 |
| Beans | Sow outdoors: Apr 29 – May 6 |
| Sweet corn | Sow outdoors: Apr 29 – May 6 |
| Cucumbers | Sow outdoors: Apr 29 – May 6 |
| Squash & zucchini | Sow outdoors: Apr 29 – May 6 |
| Basil | Start seeds indoors: Mar 11 – Mar 25 Transplant outdoors: Apr 29 – May 6 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 14 (8 weeks before the average first fall frost on Oct 9).
Useful for zone 7a 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
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 7 | Apr 22 | May 7 |
| First 32°F frost in fall is before | Oct 23 | Oct 9 | Sep 26 |
How to read it: in spring there is a 10% chance of a frost after May 7, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 26. A hard freeze (28°F) usually ends around April 6.
Hardiness zone by ZIP code in Ontario
- 97914 zone 7a
Nearby cities
- La Grande zone 6b, last frost May 6
- Pendleton zone 7a, last frost Apr 22
- Hermiston zone 7b, last frost Apr 26
- Redmond zone 6b, last frost Jun 9
- Bend zone 6b, last frost Jun 6
- The Dalles zone 7b, last frost Apr 14
- Altamont zone 6b, last frost Jun 9
- Klamath Falls zone 6b, last frost Jun 9
Questions
What growing zone is Ontario, OR?
Ontario is in USDA Plant Hardiness Zone 7a (average extreme winter low 0°F to 5°F), according to the USDA 2023 map.
When is the last frost in Ontario?
The average last spring frost (32°F) in Ontario is April 22. There is still a 10% chance of frost until May 7.
When can I plant tomatoes in Ontario?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 29 – May 6. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Ontario Ksrv, OR (USC00356294), 2.1 km (1.3 mi) from the city center, elevation 654 m, based on 17 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.