Last frost date in Wilsonville, OR

Average last frost
March 18

The average last frost in Wilsonville is March 18. By April 10 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about November 13, which leaves 243 frost-free days. An early freeze before October 27 happens one year in ten.

Safe after (10% risk)
Apr 10
Average first frost
Nov 13
Frost-free season
243 days
Hard freeze (28°F) ends
Feb 13
Next 6 nights in Wilsonville

No frost in the next 6 nights

National Weather Service forecast, updated Oct 22, 12:24 UTC

  1. ThuOct 2239°
  2. FriOct 2337°
  3. SatOct 2440°
  4. SunOct 2542°
  5. MonOct 2641°
  6. TueOct 2741°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Mar 18First frost Nov 13243 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND243 frost-free days
Frost risk through the year at N Willamette Experiment Station, 2.2 miles from Wilsonville.

Planting calendar for Wilsonville

Windows count forward or back from the average frost dates above. Click a crop for dates across Oregon.

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesMar 25–Apr 8
PumpkinsApr 1–Apr 15
SunflowersMar 18–Apr 8
CucumbersApr 1–Apr 8
CornMar 25–Apr 8
Sweet potatoesApr 8–Apr 22
WatermelonApr 1–Apr 15
Green beansMar 25–Apr 15
ZucchiniMar 25–Apr 8
OkraApr 8–Apr 22
PeppersApr 1–Apr 15
BasilMar 25–Apr 8
Butternut squashMar 25–Apr 8
CantaloupeApr 1–Apr 15
EggplantApr 1–Apr 15
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesFeb 18–Mar 4
OnionsFeb 4–Feb 25
CarrotsFeb 25–Apr 1
LettuceMar 4–Mar 25
BroccoliFeb 18–Mar 4
BeetsFeb 18–Apr 1
PeasFeb 4–Feb 18
CabbageFeb 18–Mar 4
RadishesFeb 11–Mar 25
Brussels sproutsMar 4–Mar 18
SpinachFeb 4–Feb 25
CilantroMar 4–Mar 25
KaleFeb 18–Mar 4
Collard greensFeb 18–Mar 4
TurnipsFeb 18–Mar 4
DillMar 18–Apr 1
CeleryMar 25–Apr 1
CauliflowerMar 4–Mar 18
LeeksMar 4–Mar 18
Swiss chardMar 4–Apr 1
ParsleyMar 4–Mar 25
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 30–Dec 4
GarlicOct 23–Nov 27
Daffodil bulbsOct 16–Nov 27
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesFeb 18–Mar 4
AsparagusFeb 18–Mar 4

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FFeb 22Mar 18Apr 10Oct 27Nov 13Dec 6
Hard freeze, 28°FDec 30Feb 13Mar 10Nov 9Dec 1Dec 31

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 N Willamette Experiment Station (USC00356151) sits 2.2 miles from the center of Wilsonville at 150 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 Wilsonville, OR?

The average last frost date in Wilsonville is March 18, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after April 10.

When is the first frost in Wilsonville?

The first frost in fall usually comes around November 13. One year in ten it arrives before October 27.

How long is the growing season in Wilsonville?

About 243 days between the average last and first frost.

When should I plant tomatoes in Wilsonville?

Plant tomato seedlings outside from March 25 to April 8. Start seeds indoors six to eight weeks earlier.

Nearby in Oregon

All 34 cities in Oregon