Frost dates for 97870Richland, OR
The average last spring frost in Richland is May 15 and the average first fall frost is September 24, giving a typical growing season of about 130 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 15
- Average first fall frost
- Sep 24
- Growing season
- 130 days
Safer after Jun 2 (1-in-10 risk)
Possible by Sep 9 (1-in-10 risk)
Last frost typically in 194 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 18 · Jun 5 · Jun 24 | Aug 28 · Sep 12 · Sep 26 | 96 days | 100% |
| Frost / freeze (32°F) | May 2 · May 15 · Jun 2 | Sep 9 · Sep 24 · Oct 6 | 130 days | 100% |
| Hard freeze (28°F) | Apr 18 · May 2 · May 16 | Sep 22 · Oct 5 · Oct 21 | 155 days | 100% |
Planting calendar for Richland
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 4 |
| 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 – Jun 14 |
| Summer squash | Sow outdoors | May 31 – Jul 15 |
| Winter squash & pumpkins | Sow outdoors | Jun 14 – Jul 15 |
| Snap beans | Sow outdoors | May 31 – Jul 7 |
| Sweet corn | Sow outdoors | May 31 – Jun 4 |
| 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) | May 25 – Jun 4 |
| Broccoli | Transplant outdoors (fall) | Jun 24 – Jul 5 |
| Cabbage | Start seeds indoors (spring) | Mar 17 – Apr 14 |
| Cabbage | Transplant outdoors (spring) | Apr 14 – May 15 |
| Cabbage | Start seeds indoors (fall) | May 15 – Jun 14 |
| Cabbage | Transplant outdoors (fall) | Jun 14 – Jul 15 |
| Leaf lettuce | Sow outdoors (spring) | Apr 14 – Jun 30 |
| Leaf lettuce | Sow outdoors (fall) | Jun 14 – Jul 31 |
| Spinach | Sow outdoors (spring) | Apr 7 – May 21 |
| Spinach | Sow outdoors (fall) | Jul 1 – Aug 5 |
| Radishes | Sow outdoors (spring) | Apr 14 – Jun 4 |
| Radishes | Sow outdoors (fall) | Jun 14 – Aug 15 |
| Kale | Sow outdoors (spring) | May 1 – May 21 |
| Kale | Sow outdoors (fall) | Jun 7 – Jul 15 |
| Carrots | Sow outdoors (spring) | May 15 – Jun 30 |
| Carrots | Sow outdoors (fall) | May 15 – Jun 30 |
| Garlic | Plant outdoors (fall) | Sep 14 – Oct 15 |
Where these dates come from
ZIP code 97870 is matched to the NOAA station Halfway, OR, 17.6 km away, at 2,653 ft elevation (74 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Halfway, OR (used) | 2,653 ft | May 15 | Sep 24 |
| Richland, OR | 2,215 ft | May 10 | Oct 1 |
| Brownlee Dam, ID | 1,844 ft | Apr 2 | Nov 5 |
| Baker City Muni Ap, OR | 3,361 ft | May 25 | Sep 15 |
Frost dates near Richland
- Halfway, OR 97834 · last May 15, first Sep 24
- Durkee, OR 97905 · last May 25, first Sep 15
- Oxbow, OR 97840 · last Apr 2, first Nov 5
- Baker City, OR 97814 · last May 25, first Sep 15
- Huntington, OR 97907 · last Apr 23, first Oct 13
- Bridgeport, OR 97819 · last May 25, first Sep 15
- Haines, OR 97833 · last May 25, first Sep 15
- Cambridge, ID 83610 · last May 15, first Sep 27
Frequently asked questions
- When is the last frost in Richland, OR?
- For ZIP code 97870, the average last spring frost (32°F) is May 15, based on NOAA 1991-2020 climate normals for the Halfway, OR weather station. There is a 1-in-10 chance of a frost after June 2.
- When is the first frost in Richland, OR?
- The average first fall frost (32°F) is September 24. There is a 1-in-10 chance of frost by September 9, so tender plants are at risk from that point on.
- How long is the growing season in 97870?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 130 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.