Last frost date in Lake Oswego, OR

Average last frost
March 18

In Lake Oswego, the last spring frost comes around March 18 in an average year. Wait until April 11 if you want 90% odds of no more frost. The first fall frost usually arrives about November 18, which leaves 244 frost-free days. An early freeze before October 30 happens one year in ten.

Safe after (10% risk)
Apr 11
Average first frost
Nov 18
Frost-free season
244 days
Hard freeze (28°F) ends
Feb 12
Next 6 nights in Lake Oswego

No frost in the next 6 nights

National Weather Service forecast, updated Oct 22, 12:57 UTC

  1. ThuOct 2241°
  2. FriOct 2338°
  3. SatOct 2441°
  4. SunOct 2544°
  5. MonOct 2642°
  6. TueOct 2742°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Mar 18First frost Nov 18244 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND244 frost-free days
Frost risk through the year at Oregon City, 6.1 miles from Lake Oswego.

Planting calendar for Lake Oswego

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 bulbsNov 4–Dec 9
GarlicOct 15–Nov 30
Daffodil bulbsOct 15–Nov 30
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 19Mar 18Apr 11Oct 30Nov 18Dec 12
Hard freeze, 28°FJan 1Feb 12Mar 7Nov 16Dec 8Jan 5

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 Oregon City (USC00356334) sits 6.1 miles from the center of Lake Oswego at 167 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 Lake Oswego, OR?

The average last frost date in Lake Oswego is March 18, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after April 11.

When is the first frost in Lake Oswego?

The first frost in fall usually comes around November 18. One year in ten it arrives before October 30.

How long is the growing season in Lake Oswego?

About 244 days between the average last and first frost.

When should I plant tomatoes in Lake Oswego?

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