Last frost date in Hillsboro, OR
In Hillsboro, the last spring frost comes around April 16 in an average year. Wait until May 3 if you want 90% odds of no more frost. The first fall frost usually arrives about October 23, which leaves 191 frost-free days. An early freeze before October 3 happens one year in ten.
- Safe after (10% risk)
- May 3
- Average first frost
- Oct 23
- Frost-free season
- 191 days
- Hard freeze (28°F) ends
- Mar 13
Frost possible in low spots Fri night, low 35°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2237°
- FriOct 2335°possible frost
- SatOct 2439°
- SunOct 2541°
- MonOct 2639°
- TueOct 2738°
Planting calendar for Hillsboro
Windows count forward or back from the average frost dates above. Click a crop for dates across Oregon.
TomatoesApr 23–May 7
PumpkinsApr 30–May 14
SunflowersApr 16–May 7
CucumbersApr 30–May 7
CornApr 23–May 7
Sweet potatoesMay 7–May 21
WatermelonApr 30–May 14
Green beansApr 23–May 14
ZucchiniApr 23–May 7
OkraMay 7–May 21
PeppersApr 30–May 14
BasilApr 23–May 7
Butternut squashApr 23–May 7
CantaloupeApr 30–May 14
EggplantApr 30–May 14
PotatoesMar 19–Apr 2
OnionsMar 5–Mar 26
CarrotsMar 26–Apr 30
LettuceApr 2–Apr 23
BroccoliMar 19–Apr 2
BeetsMar 19–Apr 30
PeasMar 5–Mar 19
CabbageMar 19–Apr 2
RadishesMar 12–Apr 23
Brussels sproutsApr 2–Apr 16
SpinachMar 5–Mar 26
CilantroApr 2–Apr 23
KaleMar 19–Apr 2
Collard greensMar 19–Apr 2
TurnipsMar 19–Apr 2
DillApr 16–Apr 30
CeleryApr 23–Apr 30
CauliflowerApr 2–Apr 16
LeeksApr 2–Apr 16
Swiss chardApr 2–Apr 30
ParsleyApr 2–Apr 23
Tulip bulbsOct 9–Nov 13
GarlicOct 2–Nov 6
Daffodil bulbsSep 25–Nov 6
StrawberriesMar 19–Apr 2
AsparagusMar 19–Apr 2Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Mar 25 | Apr 16 | May 3 | Oct 3 | Oct 23 | Nov 18 |
| Hard freeze, 28°F | Feb 15 | Mar 13 | Apr 9 | Oct 20 | Nov 12 | Dec 10 |
Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.
Where these numbers come from
NOAA station Portland-hillsboro Airport (USW00094261) sits 1.1 miles from the center of Hillsboro at 204 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.
Questions
When is the last frost in Hillsboro, OR?
The average last frost date in Hillsboro is April 16, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 3.
When is the first frost in Hillsboro?
The first frost in fall usually comes around October 23. One year in ten it arrives before October 3.
How long is the growing season in Hillsboro?
About 191 days between the average last and first frost.
When should I plant tomatoes in Hillsboro?
Plant tomato seedlings outside from April 23 to May 7. Start seeds indoors six to eight weeks earlier.
Nearby in Oregon
- AlohaFeb 11
- BethanyFeb 11
- BeavertonApr 1
- Forest GroveApr 16
- TigardApr 1
- SherwoodMar 21
- TualatinApr 1
- Lake OswegoMar 18
- PortlandFeb 25
- NewbergMar 21
- MilwaukieFeb 25
- WilsonvilleMar 18