Frost dates for 97029Grass Valley, OR
The average last spring frost in Grass Valley is May 15 and the average first fall frost is October 11, giving a typical growing season of about 147 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 15
- Average first fall frost
- Oct 11
- Growing season
- 147 days
Safer after Jun 6 (1-in-10 risk)
Possible by Sep 27 (1-in-10 risk)
Last frost typically in 196 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 15 · Jun 7 · Jun 27 | Sep 7 · Sep 29 · Oct 12 | 111 days | 100% |
| Frost / freeze (32°F) | Apr 29 · May 15 · Jun 6 | Sep 27 · Oct 11 · Oct 26 | 147 days | 100% |
| Hard freeze (28°F) | Apr 12 · Apr 30 · May 21 | Oct 6 · Oct 23 · Nov 9 | 173 days | 100% |
Planting calendar for Grass Valley
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 14 – Jun 20 |
| Tomatoes | Transplant outdoors | May 31 – Jun 21 |
| Peppers | Start seeds indoors | Apr 14 – May 15 |
| Peppers | Transplant outdoors | Jun 14 – Jul 15 |
| Eggplant | Start seeds indoors | May 1 – May 30 |
| Eggplant | Transplant outdoors | Jun 14 – Jul 15 |
| Cucumbers | Sow outdoors | Jun 14 – Jul 1 |
| Summer squash | Sow outdoors | May 31 – Jul 15 |
| Winter squash & pumpkins | Sow outdoors | Jun 14 – Jul 15 |
| Snap beans | Sow outdoors | May 31 – Jul 24 |
| Sweet corn | Sow outdoors | May 31 – Jun 21 |
| Watermelon & cantaloupe | Sow outdoors | Jun 14 – Jul 15 |
| Okra | Sow outdoors | Jun 7 – Jun 30 |
| Peas | Sow outdoors (spring) | Apr 14 – May 30 |
| Potatoes | Plant outdoors (spring) | Apr 14 – Jun 14 |
| Onions | Start seeds indoors (spring) | Mar 3 – Mar 30 |
| Onions | Transplant outdoors (spring) | May 1 – May 30 |
| Broccoli | Start seeds indoors (spring) | Mar 27 – Apr 30 |
| Broccoli | Transplant outdoors (spring) | May 1 – May 30 |
| Broccoli | Start seeds indoors (fall) | Jun 11 – Jun 21 |
| Broccoli | Transplant outdoors (fall) | Jul 11 – Jul 22 |
| Cabbage | Start seeds indoors (spring) | Mar 17 – Apr 14 |
| Cabbage | Transplant outdoors (spring) | Apr 14 – May 15 |
| Cabbage | Start seeds indoors (fall) | Jun 1 – Jul 1 |
| Cabbage | Transplant outdoors (fall) | Jul 1 – Aug 1 |
| Leaf lettuce | Sow outdoors (spring) | Apr 14 – Jun 30 |
| Leaf lettuce | Sow outdoors (fall) | Jul 1 – Aug 17 |
| Spinach | Sow outdoors (spring) | Apr 7 – May 21 |
| Spinach | Sow outdoors (fall) | Jul 18 – Aug 22 |
| Radishes | Sow outdoors (spring) | Apr 14 – Jun 4 |
| Radishes | Sow outdoors (fall) | Jul 1 – Sep 1 |
| Kale | Sow outdoors (spring) | May 1 – May 21 |
| Kale | Sow outdoors (fall) | Jun 24 – Aug 1 |
| Carrots | Sow outdoors (spring) | May 15 – Jun 30 |
| Carrots | Sow outdoors (fall) | Jun 1 – Jul 17 |
| Garlic | Plant outdoors (fall) | Oct 1 – Nov 1 |
Where these dates come from
ZIP code 97029 is matched to the NOAA station Kent, OR, 12.2 km away, at 2,710 ft elevation (249 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Kent, OR (used) | 2,710 ft | May 15 | Oct 11 |
| Moro, OR | 1,870 ft | May 12 | Oct 4 |
| Dufur, OR | 1,330 ft | May 12 | Oct 7 |
| Condon, OR | 2,881 ft | May 10 | Oct 7 |
Frost dates near Grass Valley
- Moro, OR 97039 · last May 12, first Oct 4
- Kent, OR 97033 · last May 22, first Oct 3
- Dufur, OR 97021 · last May 12, first Oct 4
- Wasco, OR 97065 · last May 12, first Oct 4
- Shaniko, OR 97057 · last May 22, first Oct 3
- Wishram, WA 98673 · last Apr 11, first Oct 26
- Tygh Valley, OR 97063 · last May 12, first Oct 4
- Rufus, OR 97050 · last Apr 11, first Oct 26
Frequently asked questions
- When is the last frost in Grass Valley, OR?
- For ZIP code 97029, the average last spring frost (32°F) is May 15, based on NOAA 1991-2020 climate normals for the Kent, OR weather station. There is a 1-in-10 chance of a frost after June 6.
- When is the first frost in Grass Valley, OR?
- The average first fall frost (32°F) is October 11. There is a 1-in-10 chance of frost by September 27, so tender plants are at risk from that point on.
- How long is the growing season in 97029?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 147 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.