Frost dates for 97133North Plains, OR
The average last spring frost in North Plains is May 8 and the average first fall frost is October 1, giving a typical growing season of about 144 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 8
- Average first fall frost
- Oct 1
- Growing season
- 144 days
Safer after May 29 (1-in-10 risk)
Possible by Sep 11 (1-in-10 risk)
Last frost typically in 188 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) | — | — | 94 days | 100% |
| Frost / freeze (32°F) | Apr 18 · May 8 · May 29 | Sep 11 · Oct 1 · Oct 28 | 144 days | 100% |
| Hard freeze (28°F) | Mar 14 · Apr 12 · May 7 | Sep 28 · Oct 21 · Nov 19 | 191 days | 100% |
Planting calendar for North Plains
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 | Apr 7 – Jun 13 |
| Tomatoes | Transplant outdoors | May 24 – Jun 11 |
| Peppers | Start seeds indoors | Apr 7 – May 8 |
| Peppers | Transplant outdoors | Jun 7 – Jul 8 |
| Eggplant | Start seeds indoors | Apr 24 – May 23 |
| Eggplant | Transplant outdoors | Jun 7 – Jul 8 |
| Cucumbers | Sow outdoors | Jun 7 – Jun 21 |
| Summer squash | Sow outdoors | May 24 – Jul 8 |
| Winter squash & pumpkins | Sow outdoors | Jun 7 – Jul 8 |
| Snap beans | Sow outdoors | May 24 – Jul 14 |
| Sweet corn | Sow outdoors | May 24 – Jun 11 |
| Watermelon & cantaloupe | Sow outdoors | Jun 7 – Jul 8 |
| Okra | Sow outdoors | May 31 – Jun 23 |
| Peas | Sow outdoors (spring) | Apr 7 – May 23 |
| Potatoes | Plant outdoors (spring) | Apr 7 – Jun 7 |
| Onions | Start seeds indoors (spring) | Feb 24 – Mar 23 |
| Onions | Transplant outdoors (spring) | Apr 24 – May 23 |
| Broccoli | Start seeds indoors (spring) | Mar 20 – Apr 23 |
| Broccoli | Transplant outdoors (spring) | Apr 24 – May 23 |
| Broccoli | Start seeds indoors (fall) | Jun 1 – Jun 11 |
| Broccoli | Transplant outdoors (fall) | Jul 1 – Jul 12 |
| Cabbage | Start seeds indoors (spring) | Mar 10 – Apr 7 |
| Cabbage | Transplant outdoors (spring) | Apr 7 – May 8 |
| Cabbage | Start seeds indoors (fall) | May 22 – Jun 21 |
| Cabbage | Transplant outdoors (fall) | Jun 21 – Jul 22 |
| Leaf lettuce | Sow outdoors (spring) | Apr 7 – Jun 23 |
| Leaf lettuce | Sow outdoors (fall) | Jun 21 – Aug 7 |
| Spinach | Sow outdoors (spring) | Mar 31 – May 14 |
| Spinach | Sow outdoors (fall) | Jul 8 – Aug 12 |
| Radishes | Sow outdoors (spring) | Apr 7 – May 28 |
| Radishes | Sow outdoors (fall) | Jun 21 – Aug 22 |
| Kale | Sow outdoors (spring) | Apr 24 – May 14 |
| Kale | Sow outdoors (fall) | Jun 14 – Jul 22 |
| Carrots | Sow outdoors (spring) | May 8 – Jun 23 |
| Carrots | Sow outdoors (fall) | May 22 – Jul 7 |
| Garlic | Plant outdoors (fall) | Sep 21 – Oct 22 |
Where these dates come from
ZIP code 97133 is matched to the NOAA station Vernonia #2, OR, 25.2 km away, at 625 ft elevation (77 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Vernonia #2, OR (used) | 625 ft | May 8 | Oct 1 |
| Portland-Hillsboro Ap, OR | 204 ft | Apr 16 | Oct 23 |
| Forest Grove, OR | 180 ft | Apr 16 | Oct 26 |
| Scappoose Ind Ap, OR | 55 ft | Apr 10 | Nov 2 |
Frost dates near North Plains
- Banks, OR 97106 · last Apr 16, first Oct 26
- Manning, OR 97125 · last Apr 16, first Oct 26
- Forest Grove, OR 97116 · last Apr 16, first Oct 26
- Scappoose, OR 97056 · last Apr 18, first Nov 7
- Portland, OR 97231 · last Apr 16, first Oct 23
- Hillsboro, OR 97124 · last Apr 16, first Oct 23
- Cornelius, OR 97113 · last Apr 16, first Oct 26
- Buxton, OR 97109 · last May 8, first Oct 1
Frequently asked questions
- When is the last frost in North Plains, OR?
- For ZIP code 97133, the average last spring frost (32°F) is May 8, based on NOAA 1991-2020 climate normals for the Vernonia #2, OR weather station. There is a 1-in-10 chance of a frost after May 29.
- When is the first frost in North Plains, OR?
- The average first fall frost (32°F) is October 1. There is a 1-in-10 chance of frost by September 11, so tender plants are at risk from that point on.
- How long is the growing season in 97133?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 144 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.