Frost dates for 97758Riley, OR
The average last spring frost in Riley is June 11 and the average first fall frost is September 28, giving a typical growing season of about 107 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 11
- Average first fall frost
- Sep 28
- Growing season
- 107 days
Safer after Jun 28 (1-in-10 risk)
Possible by Sep 3 (1-in-10 risk)
Last frost typically in 221 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) | — | — | 81 days | 100% |
| Frost / freeze (32°F) | May 18 · Jun 11 · Jun 28 | Sep 3 · Sep 28 · Oct 13 | 107 days | 100% |
| Hard freeze (28°F) | Apr 27 · May 24 · Jun 18 | Sep 22 · Oct 13 · Oct 28 | 139 days | 100% |
Planting calendar for Riley
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 | May 11 – Jul 17 |
| Tomatoes | Transplant outdoors | Jun 27 – Jun 8 |
| Peppers | Start seeds indoors | May 11 – Jun 11 |
| Peppers | Transplant outdoors | Jul 11 – Aug 11 |
| Eggplant | Start seeds indoors | May 28 – Jun 26 |
| Eggplant | Transplant outdoors | Jul 11 – Aug 11 |
| Cucumbers | Sow outdoors | Jul 11 – Jun 18 |
| Summer squash | Sow outdoors | Jun 27 – Aug 11 |
| Winter squash & pumpkins | Sow outdoors | Jul 11 – Aug 11 |
| Snap beans | Sow outdoors | Jun 27 – Jul 11 |
| Sweet corn | Sow outdoors | Jun 27 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jul 11 – Aug 11 |
| Okra | Sow outdoors | Jul 4 – Jul 27 |
| Peas | Sow outdoors (spring) | May 11 – Jun 26 |
| Potatoes | Plant outdoors (spring) | May 11 – Jul 11 |
| Onions | Start seeds indoors (spring) | Mar 30 – Apr 26 |
| Onions | Transplant outdoors (spring) | May 28 – Jun 26 |
| Broccoli | Start seeds indoors (spring) | Apr 23 – May 27 |
| Broccoli | Transplant outdoors (spring) | May 28 – Jun 26 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Apr 13 – May 11 |
| Cabbage | Transplant outdoors (spring) | May 11 – Jun 11 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | May 11 – Jul 27 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | May 4 – Jun 17 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | May 11 – Jul 1 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | May 28 – Jun 17 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | Jun 11 – Jul 27 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 97758 is matched to the NOAA station Squaw Butte-Northern Great Bas, OR, 16.8 km away, at 4,660 ft elevation (497 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Squaw Butte-Northern Great Bas, OR (used) | 4,660 ft | Jun 11 | Sep 28 |
| Riley 10 Wsw, OR | 4,583 ft | Jun 11 | Sep 11 |
| Alkali Lake, OR | 4,332 ft | Jun 10 | Sep 14 |
| O O Rch, OR | 4,136 ft | Jun 11 | Sep 6 |
Frost dates near Riley
- Christmas Valley, OR 97641 · last —, first —
- Brothers, OR 97712 · last —, first —
- Hines, OR 97738 · last Jun 11, first Sep 6
- Burns, OR 97720 · last Jun 11, first Sep 6
- Princeton, OR 97721 · last Jun 11, first Sep 6
- Post, OR 97752 · last Jun 2, first Sep 17
- Summer Lake, OR 97640 · last Jun 8, first Sep 15
- Paulina, OR 97751 · last Jun 2, first Sep 17
Frequently asked questions
- When is the last frost in Riley, OR?
- For ZIP code 97758, the average last spring frost (32°F) is June 11, based on NOAA 1991-2020 climate normals for the Squaw Butte-Northern Great Bas, OR weather station. There is a 1-in-10 chance of a frost after June 28.
- When is the first frost in Riley, OR?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 3, so tender plants are at risk from that point on.
- How long is the growing season in 97758?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 107 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.