Frost dates for 97830Fossil, OR
The average last spring frost in Fossil is May 22 and the average first fall frost is October 4, giving a typical growing season of about 135 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 22
- Average first fall frost
- Oct 4
- Growing season
- 135 days
Safer after Jun 11 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 201 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) | May 27 · Jun 14 · Jun 30 | Sep 1 · Sep 19 · Oct 5 | 96 days | 100% |
| Frost / freeze (32°F) | May 1 · May 22 · Jun 11 | Sep 16 · Oct 4 · Oct 20 | 135 days | 100% |
| Hard freeze (28°F) | Apr 11 · Apr 30 · May 18 | Oct 4 · Oct 22 · Nov 7 | 173 days | 100% |
Planting calendar for Fossil
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 21 – Jun 27 |
| Tomatoes | Transplant outdoors | Jun 7 – Jun 14 |
| Peppers | Start seeds indoors | Apr 21 – May 22 |
| Peppers | Transplant outdoors | Jun 21 – Jul 22 |
| Eggplant | Start seeds indoors | May 8 – Jun 6 |
| Eggplant | Transplant outdoors | Jun 21 – Jul 22 |
| Cucumbers | Sow outdoors | Jun 21 – Jun 24 |
| Summer squash | Sow outdoors | Jun 7 – Jul 22 |
| Winter squash & pumpkins | Sow outdoors | Jun 21 – Jul 22 |
| Snap beans | Sow outdoors | Jun 7 – Jul 17 |
| Sweet corn | Sow outdoors | Jun 7 – Jun 14 |
| Watermelon & cantaloupe | Sow outdoors | Jun 21 – Jul 22 |
| Okra | Sow outdoors | Jun 14 – Jul 7 |
| Peas | Sow outdoors (spring) | Apr 21 – Jun 6 |
| Potatoes | Plant outdoors (spring) | Apr 21 – Jun 21 |
| Onions | Start seeds indoors (spring) | Mar 10 – Apr 6 |
| Onions | Transplant outdoors (spring) | May 8 – Jun 6 |
| Broccoli | Start seeds indoors (spring) | Apr 3 – May 7 |
| Broccoli | Transplant outdoors (spring) | May 8 – Jun 6 |
| Broccoli | Start seeds indoors (fall) | Jun 4 – Jun 14 |
| Broccoli | Transplant outdoors (fall) | Jul 4 – Jul 15 |
| Cabbage | Start seeds indoors (spring) | Mar 24 – Apr 21 |
| Cabbage | Transplant outdoors (spring) | Apr 21 – May 22 |
| Cabbage | Start seeds indoors (fall) | May 25 – Jun 24 |
| Cabbage | Transplant outdoors (fall) | Jun 24 – Jul 25 |
| Leaf lettuce | Sow outdoors (spring) | Apr 21 – Jul 7 |
| Leaf lettuce | Sow outdoors (fall) | Jun 24 – Aug 10 |
| Spinach | Sow outdoors (spring) | Apr 14 – May 28 |
| Spinach | Sow outdoors (fall) | Jul 11 – Aug 15 |
| Radishes | Sow outdoors (spring) | Apr 21 – Jun 11 |
| Radishes | Sow outdoors (fall) | Jun 24 – Aug 25 |
| Kale | Sow outdoors (spring) | May 8 – May 28 |
| Kale | Sow outdoors (fall) | Jun 17 – Jul 25 |
| Carrots | Sow outdoors (spring) | May 22 – Jul 7 |
| Carrots | Sow outdoors (fall) | May 25 – Jul 10 |
| Garlic | Plant outdoors (fall) | Sep 24 – Oct 25 |
Where these dates come from
ZIP code 97830 is matched to the NOAA station Mitchell 2 E, OR, 40.1 km away, at 3,320 ft elevation (305 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Mitchell 2 E, OR (used) | 3,320 ft | May 22 | Oct 4 |
| Fossil, OR | 2,650 ft | Jun 3 | Sep 14 |
| Condon, OR | 2,881 ft | May 10 | Oct 7 |
| Antelope 6 Ssw, OR | 3,030 ft | May 22 | Oct 3 |
Frost dates near Fossil
- Spray, OR 97874 · last Apr 30, first Oct 14
- Condon, OR 97823 · last May 10, first Oct 7
- Mitchell, OR 97750 · last May 22, first Oct 4
- Kent, OR 97033 · last May 22, first Oct 3
- Kimberly, OR 97848 · last Jun 5, first Sep 14
- Shaniko, OR 97057 · last May 22, first Oct 3
- Ashwood, OR 97711 · last —, first —
- Antelope, OR 97001 · last May 22, first Oct 3
Frequently asked questions
- When is the last frost in Fossil, OR?
- For ZIP code 97830, the average last spring frost (32°F) is May 22, based on NOAA 1991-2020 climate normals for the Mitchell 2 E, OR weather station. There is a 1-in-10 chance of a frost after June 11.
- When is the first frost in Fossil, OR?
- The average first fall frost (32°F) is October 4. There is a 1-in-10 chance of frost by September 16, so tender plants are at risk from that point on.
- How long is the growing season in 97830?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 135 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.