Riley, OR frost dates
Last spring frostJun 11median date
First fall frostSep 28median date
Growing season109 daysfrost-free
Hardiness zone6aZone 6a
How Riley compares
- In 8 years out of 10, the last spring frost in Riley falls between May 18 and June 28, a 41-day window. The first fall frost falls between September 3 and October 13.
- The median last frost is 56 days later than the Oregon median of Apr 16.
- Its 109-day growing season is longer than 8% of the 345 Oregon places with a regular frost season (state median 193 days).
- The last frost is 43 days later than the zone 6a median of Apr 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6a chart.
- The weather station records an average of 180 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 18 |
| 50% (median) | June 11 |
| 10% (safe for tender plants) | June 28 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 3 |
| 50% (median) | September 28 |
| 90% (late) | October 13 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Riley, OR
Riley, OR frost dates — last frost Jun 11, first frost Sep 28, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Mar 19 to Apr 2Transplant outside: May 14 to May 28
Start indoors: Apr 2 to Apr 16Transplant outside: Jun 25 to Jul 9
Start indoors: Apr 2 to Apr 16Transplant outside: Jun 25 to Jul 9
Start indoors: Apr 16 to Apr 30Transplant outside: Jun 18 to Jul 2
Start indoors: Apr 16 to Apr 30Transplant outside: May 21 to Jun 4Sow outdoors: May 14 to Jun 18Plant for fall: Aug 3 to Aug 31
Start indoors: Apr 16 to Apr 30Transplant outside: May 14 to May 28Sow outdoors: May 14 to May 28Plant for fall: Jul 20 to Aug 10
Start indoors: Apr 16 to Apr 30Transplant outside: May 28 to Jun 11
Start indoors: Apr 16 to Apr 30Transplant outside: May 21 to Jun 4
Start indoors: Apr 16 to Apr 30Transplant outside: May 28 to Jun 11
Start indoors: Apr 30 to May 14Transplant outside: Jul 2 to Jul 16Sow outdoors: Jul 2 to Jul 16
Start indoors: Apr 30 to May 14Transplant outside: Jun 18 to Jul 2
Sow outdoors: Apr 30 to May 21Plant for fall: Jul 6 to Jul 27
Sow outdoors: Apr 30 to May 21Plant for fall: Aug 3 to Aug 24
Sow outdoors: May 7 to Jun 18Plant for fall: Aug 17 to Sep 7
Start indoors: May 14 to May 21Transplant outside: Jun 25 to Jul 2Sow outdoors: Jun 18 to Jul 2
Start indoors: May 14 to May 21Sow outdoors: Jun 18 to Jul 2Plant for fall: Jul 20 to Aug 3
Start indoors: May 14 to May 21Sow outdoors: Jun 18 to Jul 2
Start indoors: May 14 to May 21Transplant outside: Jun 25 to Jul 9
Sow outdoors: May 21 to Jun 18Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 21 to Jun 18Plant for fall: Jul 20 to Aug 3
Sow outdoors: May 21 to Jun 11
Sow outdoors: May 28 to Jun 25Plant for fall: Jul 20 to Aug 3
Sow outdoors: May 28 to Jun 18Plant for fall: Aug 3 to Aug 24
Sow outdoors: Jun 18 to Jul 9
Sow outdoors: Jun 18 to Jul 2
Transplant outside: Jun 25 to Jul 16
Plant for fall: Sep 14 to Oct 19
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Riley, OR
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 19 – Apr 2 | May 14 – May 28 | — | — |
| Peppers | Apr 2 – Apr 16 | Jun 25 – Jul 9 | — | — |
| Eggplant | Apr 2 – Apr 16 | Jun 25 – Jul 9 | — | — |
| Tomatoes | Apr 16 – Apr 30 | Jun 18 – Jul 2 | — | — |
| Lettuce | Apr 16 – Apr 30 | May 21 – Jun 4 | May 14 – Jun 18 | Aug 3 – Aug 31 |
| Kale | Apr 16 – Apr 30 | May 14 – May 28 | May 14 – May 28 | Jul 20 – Aug 10 |
| Broccoli | Apr 16 – Apr 30 | May 28 – Jun 11 | — | — |
| Cabbage | Apr 16 – Apr 30 | May 21 – Jun 4 | — | — |
| Cauliflower | Apr 16 – Apr 30 | May 28 – Jun 11 | — | — |
| Okra | Apr 30 – May 14 | Jul 2 – Jul 16 | Jul 2 – Jul 16 | — |
| Basil | Apr 30 – May 14 | Jun 18 – Jul 2 | — | — |
| Peas | — | — | Apr 30 – May 21 | Jul 6 – Jul 27 |
| Spinach | — | — | Apr 30 – May 21 | Aug 3 – Aug 24 |
| Radishes | — | — | May 7 – Jun 18 | Aug 17 – Sep 7 |
| Cucumbers | May 14 – May 21 | Jun 25 – Jul 2 | Jun 18 – Jul 2 | — |
| Zucchini & Summer Squash | May 14 – May 21 | — | Jun 18 – Jul 2 | Jul 20 – Aug 3 |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 109 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | May 14 – May 21 | — | Jun 18 – Jul 2 | — |
| Melons & Watermelon | May 14 – May 21 | Jun 25 – Jul 9 | — | — |
| Carrots | — | — | May 21 – Jun 18 | Jul 6 – Jul 20 |
| Beets | — | — | May 21 – Jun 18 | Jul 20 – Aug 3 |
| Potatoes | — | — | May 21 – Jun 11 | — |
| Swiss Chard | — | — | May 28 – Jun 25 | Jul 20 – Aug 3 |
| Cilantro | — | — | May 28 – Jun 18 | Aug 3 – Aug 24 |
| Green Beans | — | — | Jun 18 – Jul 9 | — |
| Sweet Corn | — | — | Jun 18 – Jul 2 | — |
| Sweet Potatoes Warning: Your frost-free season is about 109 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 25 – Jul 16 | — | — |
| Garlic | — | — | — | Sep 14 – Oct 19 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Squaw Butte-Northern Great Bas, OR weather station, 17 km away (elevation 4,659 ft (1,420 m)).
Frost dates near Riley
- Christmas Valley frost any month
- Brothers frost any month
- Hines Jun 11 · Sep 6
- Burns Jun 11 · Sep 6
- Princeton May 29 · Sep 18
- Post Jun 2 · Sep 17
- Summer Lake Jun 8 · Sep 15
- Paulina frost any month
- Paisley Jun 6 · Sep 14
- Silver Lake frost any month
Frequently asked questions
When is the last frost in Riley, OR?
The median last spring frost in Riley, OR is June 11. There is still about a 10% chance of frost after June 28, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Riley, OR?
The median first fall frost is September 28, with about a 10% chance of frost before September 3.
How long is the growing season in Riley, OR?
About 109 days between the median last spring frost and first fall frost.
What planting zone is Riley, OR?
Riley, OR is in USDA hardiness zone 6a.