Frost dates for 97070Wilsonville, OR
The average last spring frost in Wilsonville is March 18 and the average first fall frost is November 13, giving a typical growing season of about 243 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 18
- Average first fall frost
- Nov 13
- Growing season
- 243 days
Safer after Apr 10 (1-in-10 risk)
Possible by Oct 27 (1-in-10 risk)
First frost typically in 13 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Mar 29 · Apr 17 · May 6 | Oct 11 · Oct 27 · Nov 15 | 193 days | 100% |
| Frost / freeze (32°F) | Feb 22 · Mar 18 · Apr 10 | Oct 27 · Nov 13 · Dec 6 | 243 days | 100% |
| Hard freeze (28°F) | Dec 30 · Feb 13 · Mar 10 | Nov 9 · Dec 1 · Dec 31 | 298 days | 98% |
Planting calendar for Wilsonville
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Feb 15 – Apr 23 |
| Tomatoes | Transplant outdoors | Apr 3 – Jul 24 |
| Peppers | Start seeds indoors | Feb 15 – Mar 18 |
| Peppers | Transplant outdoors | Apr 17 – May 18 |
| Eggplant | Start seeds indoors | Mar 4 – Apr 2 |
| Eggplant | Transplant outdoors | Apr 17 – May 18 |
| Cucumbers | Sow outdoors | Apr 17 – Aug 3 |
| Summer squash | Sow outdoors | Apr 3 – May 18 |
| Winter squash & pumpkins | Sow outdoors | Apr 17 – May 18 |
| Snap beans | Sow outdoors | Apr 3 – Aug 26 |
| Sweet corn | Sow outdoors | Apr 3 – Jul 24 |
| Watermelon & cantaloupe | Sow outdoors | Apr 17 – May 18 |
| Okra | Sow outdoors | Apr 10 – May 3 |
| Peas | Sow outdoors (spring) | Feb 15 – Apr 2 |
| Potatoes | Plant outdoors (spring) | Feb 15 – Apr 17 |
| Onions | Start seeds indoors (spring) | Jan 4 – Jan 31 |
| Onions | Transplant outdoors (spring) | Mar 4 – Apr 2 |
| Broccoli | Start seeds indoors (spring) | Jan 28 – Mar 3 |
| Broccoli | Transplant outdoors (spring) | Mar 4 – Apr 2 |
| Broccoli | Start seeds indoors (fall) | Jul 14 – Jul 24 |
| Broccoli | Transplant outdoors (fall) | Aug 13 – Aug 24 |
| Cabbage | Start seeds indoors (spring) | Jan 18 – Feb 15 |
| Cabbage | Transplant outdoors (spring) | Feb 15 – Mar 18 |
| Cabbage | Start seeds indoors (fall) | Jul 4 – Aug 3 |
| Cabbage | Transplant outdoors (fall) | Aug 3 – Sep 3 |
| Leaf lettuce | Sow outdoors (spring) | Feb 15 – May 3 |
| Leaf lettuce | Sow outdoors (fall) | Aug 3 – Sep 19 |
| Spinach | Sow outdoors (spring) | Feb 8 – Mar 24 |
| Spinach | Sow outdoors (fall) | Aug 20 – Sep 24 |
| Radishes | Sow outdoors (spring) | Feb 15 – Apr 7 |
| Radishes | Sow outdoors (fall) | Aug 3 – Oct 4 |
| Kale | Sow outdoors (spring) | Mar 4 – Mar 24 |
| Kale | Sow outdoors (fall) | Jul 27 – Sep 3 |
| Carrots | Sow outdoors (spring) | Mar 18 – May 3 |
| Carrots | Sow outdoors (fall) | Jul 4 – Aug 19 |
| Garlic | Plant outdoors (fall) | Nov 3 – Dec 4 |
Where these dates come from
ZIP code 97070 is matched to the NOAA station N Willamette Exp Stn, OR, 2.4 km away, at 150 ft elevation (8 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| N Willamette Exp Stn, OR (used) | 150 ft | Mar 18 | Nov 13 |
| Aurora State Ap, OR | 196 ft | Mar 16 | Nov 14 |
| Rex 1 S, OR | 515 ft | Mar 21 | Nov 22 |
| Oregon City, OR | 167 ft | Mar 18 | Nov 18 |
Frost dates near Wilsonville
- Aurora, OR 97002 · last Mar 16, first Nov 14
- Tualatin, OR 97062 · last Apr 1, first Nov 6
- Canby, OR 97013 · last Mar 16, first Nov 14
- Sherwood, OR 97140 · last Mar 16, first Nov 14
- Donald, OR 97020 · last Mar 16, first Nov 14
- West Linn, OR 97068 · last Mar 18, first Nov 18
- Portland, OR 97224 · last Apr 1, first Nov 6
- Hubbard, OR 97032 · last Mar 16, first Nov 14
Frequently asked questions
- When is the last frost in Wilsonville, OR?
- For ZIP code 97070, the average last spring frost (32°F) is March 18, based on NOAA 1991-2020 climate normals for the N Willamette Exp Stn, OR weather station. There is a 1-in-10 chance of a frost after April 10.
- When is the first frost in Wilsonville, OR?
- The average first fall frost (32°F) is November 13. There is a 1-in-10 chance of frost by October 27, so tender plants are at risk from that point on.
- How long is the growing season in 97070?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 243 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.