Hillsboro, OR frost dates
Last spring frostApr 16median date
First fall frostOct 23median date
Growing season190 daysfrost-free
Hardiness zone8bZone 8b
How Hillsboro compares
- In 8 years out of 10, the last spring frost in Hillsboro falls between March 25 and May 3, a 39-day window. The first fall frost falls between October 3 and November 18.
- The median last frost is the same as the Oregon median of Apr 16.
- Its 190-day growing season is longer than 45% of the 345 Oregon places with a regular frost season (state median 193 days).
- The last frost is 31 days later than the zone 8b median of Mar 16. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 8b chart.
- The weather station records an average of 64 nights a year at or below 32°F.
- Compared with Portland, OR, 23 km away, the last frost here is 50 days later than there and the growing season is 89 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | March 25 |
| 50% (median) | April 16 |
| 10% (safe for tender plants) | May 3 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 3 |
| 50% (median) | October 23 |
| 90% (late) | November 18 |
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 Hillsboro, OR
Hillsboro, OR frost dates — last frost Apr 16, first frost Oct 23, zone 8b. whenisthelastfrost.com
Crop
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Start indoors: Jan 22 to Feb 5Transplant outside: Mar 19 to Apr 2
Start indoors: Feb 5 to Feb 19Transplant outside: Apr 30 to May 14
Start indoors: Feb 5 to Feb 19Transplant outside: Apr 30 to May 14
Start indoors: Feb 19 to Mar 5Transplant outside: Apr 23 to May 7
Start indoors: Feb 19 to Mar 5Transplant outside: Mar 26 to Apr 9Sow outdoors: Mar 19 to Apr 23Plant for fall: Aug 28 to Sep 25
Start indoors: Feb 19 to Mar 5Transplant outside: Mar 19 to Apr 2Sow outdoors: Mar 19 to Apr 2Plant for fall: Aug 14 to Sep 4
Start indoors: Feb 19 to Mar 5Transplant outside: Apr 2 to Apr 16Plant for fall: Jul 17 to Aug 7
Start indoors: Feb 19 to Mar 5Transplant outside: Mar 26 to Apr 9Plant for fall: Jul 17 to Aug 7
Start indoors: Feb 19 to Mar 5Transplant outside: Apr 2 to Apr 16Plant for fall: Jul 17 to Aug 7
Start indoors: Mar 5 to Mar 19Transplant outside: May 7 to May 21Sow outdoors: May 7 to May 21
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 23 to May 7
Sow outdoors: Mar 5 to Mar 26Plant for fall: Jul 31 to Aug 21
Sow outdoors: Mar 5 to Mar 26Plant for fall: Aug 28 to Sep 18
Sow outdoors: Mar 12 to Apr 23Plant for fall: Sep 11 to Oct 2
Start indoors: Mar 19 to Mar 26Transplant outside: Apr 30 to May 7Sow outdoors: Apr 23 to May 7Plant for fall: Aug 7 to Aug 21
Start indoors: Mar 19 to Mar 26Sow outdoors: Apr 23 to May 7Plant for fall: Aug 14 to Aug 28
Start indoors: Mar 19 to Mar 26Sow outdoors: Apr 23 to May 7
Start indoors: Mar 19 to Mar 26Transplant outside: Apr 30 to May 14
Sow outdoors: Mar 26 to Apr 23Plant for fall: Jul 31 to Aug 14
Sow outdoors: Mar 26 to Apr 23Plant for fall: Aug 14 to Aug 28
Sow outdoors: Mar 26 to Apr 16
Sow outdoors: Apr 2 to Apr 30Plant for fall: Aug 14 to Aug 28
Sow outdoors: Apr 2 to Apr 23Plant for fall: Aug 28 to Sep 18
Sow outdoors: Apr 23 to May 14Plant for fall: Aug 7 to Aug 21
Sow outdoors: Apr 23 to May 7
Transplant outside: Apr 30 to May 21
Plant for fall: Oct 9 to Nov 13
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Hillsboro, OR
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 22 – Feb 5 | Mar 19 – Apr 2 | — | — |
| Peppers | Feb 5 – Feb 19 | Apr 30 – May 14 | — | — |
| Eggplant | Feb 5 – Feb 19 | Apr 30 – May 14 | — | — |
| Tomatoes | Feb 19 – Mar 5 | Apr 23 – May 7 | — | — |
| Lettuce | Feb 19 – Mar 5 | Mar 26 – Apr 9 | Mar 19 – Apr 23 | Aug 28 – Sep 25 |
| Kale | Feb 19 – Mar 5 | Mar 19 – Apr 2 | Mar 19 – Apr 2 | Aug 14 – Sep 4 |
| Broccoli | Feb 19 – Mar 5 | Apr 2 – Apr 16 | — | Jul 17 – Aug 7 |
| Cabbage | Feb 19 – Mar 5 | Mar 26 – Apr 9 | — | Jul 17 – Aug 7 |
| Cauliflower | Feb 19 – Mar 5 | Apr 2 – Apr 16 | — | Jul 17 – Aug 7 |
| Okra | Mar 5 – Mar 19 | May 7 – May 21 | May 7 – May 21 | — |
| Basil | Mar 5 – Mar 19 | Apr 23 – May 7 | — | — |
| Peas | — | — | Mar 5 – Mar 26 | Jul 31 – Aug 21 |
| Spinach | — | — | Mar 5 – Mar 26 | Aug 28 – Sep 18 |
| Radishes | — | — | Mar 12 – Apr 23 | Sep 11 – Oct 2 |
| Cucumbers | Mar 19 – Mar 26 | Apr 30 – May 7 | Apr 23 – May 7 | Aug 7 – Aug 21 |
| Zucchini & Summer Squash | Mar 19 – Mar 26 | — | Apr 23 – May 7 | Aug 14 – Aug 28 |
| Winter Squash & Pumpkins | Mar 19 – Mar 26 | — | Apr 23 – May 7 | — |
| Melons & Watermelon | Mar 19 – Mar 26 | Apr 30 – May 14 | — | — |
| Carrots | — | — | Mar 26 – Apr 23 | Jul 31 – Aug 14 |
| Beets | — | — | Mar 26 – Apr 23 | Aug 14 – Aug 28 |
| Potatoes | — | — | Mar 26 – Apr 16 | — |
| Swiss Chard | — | — | Apr 2 – Apr 30 | Aug 14 – Aug 28 |
| Cilantro | — | — | Apr 2 – Apr 23 | Aug 28 – Sep 18 |
| Green Beans | — | — | Apr 23 – May 14 | Aug 7 – Aug 21 |
| Sweet Corn | — | — | Apr 23 – May 7 | — |
| Sweet Potatoes | — | Apr 30 – May 21 | — | — |
| Garlic | — | — | — | Oct 9 – Nov 13 |
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 Portland-Hillsboro Ap, OR weather station, 2 km away (elevation 203 ft (62 m)).
ZIP codes in Hillsboro: 97123 97124 97129
Frost dates near Hillsboro
- Cornelius Apr 16 · Oct 26
- Beaverton Feb 11 · Dec 5
- North Plains Apr 16 · Oct 23
- Gaston Apr 16 · Oct 26
- Banks Apr 16 · Oct 26
- Forest Grove Apr 16 · Oct 26
- Sherwood Mar 21 · Nov 22
- Manning Apr 16 · Oct 26
- Gales Creek Apr 16 · Oct 26
- Tualatin Apr 1 · Nov 6
Frequently asked questions
When is the last frost in Hillsboro, OR?
The median last spring frost in Hillsboro, OR is April 16. There is still about a 10% chance of frost after May 3, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Hillsboro, OR?
The median first fall frost is October 23, with about a 10% chance of frost before October 3.
How long is the growing season in Hillsboro, OR?
About 190 days between the median last spring frost and first fall frost.
What planting zone is Hillsboro, OR?
Hillsboro, OR is in USDA hardiness zone 8b.