Union, OR frost dates
Last spring frostMay 11median date
First fall frostSep 26median date
Growing season138 daysfrost-free
Hardiness zone6bZone 6b
How Union compares
- In 8 years out of 10, the last spring frost in Union falls between April 26 and May 31, a 35-day window. The first fall frost falls between September 9 and October 10.
- The median last frost is 25 days later than the Oregon median of Apr 16.
- Its 138-day growing season is longer than 17% of the 345 Oregon places with a regular frost season (state median 193 days).
- The last frost is 19 days later than the zone 6b median of Apr 22. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6b chart.
- The weather station records an average of 135 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 26 |
| 50% (median) | May 11 |
| 10% (safe for tender plants) | May 31 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 9 |
| 50% (median) | September 26 |
| 90% (late) | October 10 |
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 Union, OR
Union, OR frost dates — last frost May 11, first frost Sep 26, zone 6b. whenisthelastfrost.com
Crop
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Start indoors: Feb 16 to Mar 2Transplant outside: Apr 13 to Apr 27
Start indoors: Mar 2 to Mar 16Transplant outside: May 25 to Jun 8
Start indoors: Mar 2 to Mar 16Transplant outside: May 25 to Jun 8
Start indoors: Mar 16 to Mar 30Transplant outside: May 18 to Jun 1
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 20 to May 4Sow outdoors: Apr 13 to May 18Plant for fall: Aug 1 to Aug 29
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 13 to Apr 27Sow outdoors: Apr 13 to Apr 27Plant for fall: Jul 18 to Aug 8
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 27 to May 11Plant for fall: Jun 20 to Jul 11
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 20 to May 4Plant for fall: Jun 20 to Jul 11
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 27 to May 11Plant for fall: Jun 20 to Jul 11
Start indoors: Mar 30 to Apr 13Transplant outside: Jun 1 to Jun 15Sow outdoors: Jun 1 to Jun 15
Start indoors: Mar 30 to Apr 13Transplant outside: May 18 to Jun 1
Sow outdoors: Mar 30 to Apr 20Plant for fall: Jul 4 to Jul 25
Sow outdoors: Mar 30 to Apr 20Plant for fall: Aug 1 to Aug 22
Sow outdoors: Apr 6 to May 18Plant for fall: Aug 15 to Sep 5
Start indoors: Apr 13 to Apr 20Transplant outside: May 25 to Jun 1Sow outdoors: May 18 to Jun 1Plant for fall: Jul 11 to Jul 25
Start indoors: Apr 13 to Apr 20Sow outdoors: May 18 to Jun 1Plant for fall: Jul 18 to Aug 1
Start indoors: Apr 13 to Apr 20Sow outdoors: May 18 to Jun 1
Start indoors: Apr 13 to Apr 20Transplant outside: May 25 to Jun 8
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 4 to Jul 18
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 18 to Aug 1
Sow outdoors: Apr 20 to May 11
Sow outdoors: Apr 27 to May 25Plant for fall: Jul 18 to Aug 1
Sow outdoors: Apr 27 to May 18Plant for fall: Aug 1 to Aug 22
Sow outdoors: May 18 to Jun 8Plant for fall: Jul 11 to Jul 25
Sow outdoors: May 18 to Jun 1
Transplant outside: May 25 to Jun 15
Plant for fall: Sep 12 to Oct 17
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Union, OR
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 16 – Mar 2 | Apr 13 – Apr 27 | — | — |
| Peppers | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Eggplant | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Tomatoes | Mar 16 – Mar 30 | May 18 – Jun 1 | — | — |
| Lettuce | Mar 16 – Mar 30 | Apr 20 – May 4 | Apr 13 – May 18 | Aug 1 – Aug 29 |
| Kale | Mar 16 – Mar 30 | Apr 13 – Apr 27 | Apr 13 – Apr 27 | Jul 18 – Aug 8 |
| Broccoli | Mar 16 – Mar 30 | Apr 27 – May 11 | — | Jun 20 – Jul 11 |
| Cabbage | Mar 16 – Mar 30 | Apr 20 – May 4 | — | Jun 20 – Jul 11 |
| Cauliflower | Mar 16 – Mar 30 | Apr 27 – May 11 | — | Jun 20 – Jul 11 |
| Okra | Mar 30 – Apr 13 | Jun 1 – Jun 15 | Jun 1 – Jun 15 | — |
| Basil | Mar 30 – Apr 13 | May 18 – Jun 1 | — | — |
| Peas | — | — | Mar 30 – Apr 20 | Jul 4 – Jul 25 |
| Spinach | — | — | Mar 30 – Apr 20 | Aug 1 – Aug 22 |
| Radishes | — | — | Apr 6 – May 18 | Aug 15 – Sep 5 |
| Cucumbers | Apr 13 – Apr 20 | May 25 – Jun 1 | May 18 – Jun 1 | Jul 11 – Jul 25 |
| Zucchini & Summer Squash | Apr 13 – Apr 20 | — | May 18 – Jun 1 | Jul 18 – Aug 1 |
| Winter Squash & Pumpkins | Apr 13 – Apr 20 | — | May 18 – Jun 1 | — |
| Melons & Watermelon | Apr 13 – Apr 20 | May 25 – Jun 8 | — | — |
| Carrots | — | — | Apr 20 – May 18 | Jul 4 – Jul 18 |
| Beets | — | — | Apr 20 – May 18 | Jul 18 – Aug 1 |
| Potatoes | — | — | Apr 20 – May 11 | — |
| Swiss Chard | — | — | Apr 27 – May 25 | Jul 18 – Aug 1 |
| Cilantro | — | — | Apr 27 – May 18 | Aug 1 – Aug 22 |
| Green Beans | — | — | May 18 – Jun 8 | Jul 11 – Jul 25 |
| Sweet Corn | — | — | May 18 – Jun 1 | — |
| Sweet Potatoes | — | May 25 – Jun 15 | — | — |
| Garlic | — | — | — | Sep 12 – Oct 17 |
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 Union, OR weather station, about 1 km away (elevation 2,776 ft (846 m)).
Frost dates near Union
- Cove May 11 · Sep 26
- North Powder May 11 · Sep 26
- La Grande May 6 · Oct 1
- Imbler May 24 · Sep 18
- Summerville May 24 · Sep 18
- Haines May 25 · Sep 15
- Elgin May 24 · Sep 18
- Lostine Jun 7 · Sep 9
- Baker City May 25 · Sep 15
- Wallowa Jun 7 · Sep 9
Frequently asked questions
When is the last frost in Union, OR?
The median last spring frost in Union, OR is May 11. There is still about a 10% chance of frost after May 31, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Union, OR?
The median first fall frost is September 26, with about a 10% chance of frost before September 9.
How long is the growing season in Union, OR?
About 138 days between the median last spring frost and first fall frost.
What planting zone is Union, OR?
Union, OR is in USDA hardiness zone 6b.