Last frost date in Williamsport, PA
The average last frost in Williamsport is April 25. By May 12 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 24, which leaves 181 frost-free days. An early freeze before October 8 happens one year in ten.
- Safe after (10% risk)
- May 12
- Average first frost
- Oct 24
- Frost-free season
- 181 days
- Hard freeze (28°F) ends
- Apr 10
Frost likely Fri night, low 30°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2238°
- FriOct 2330°frost
- SatOct 2432°frost
- SunOct 2537°
- MonOct 2644°
- TueOct 2742°
- WedOct 2842°
Planting calendar for Williamsport
Windows count forward or back from the average frost dates above. Click a crop for dates across Pennsylvania.
TomatoesMay 2–May 16
PumpkinsMay 9–May 23
SunflowersApr 25–May 16
CucumbersMay 9–May 16
CornMay 2–May 16
Sweet potatoesMay 16–May 30
WatermelonMay 9–May 23
Green beansMay 2–May 23
ZucchiniMay 2–May 16
OkraMay 16–May 30
PeppersMay 9–May 23
BasilMay 2–May 16
Butternut squashMay 2–May 16
CantaloupeMay 9–May 23
EggplantMay 9–May 23
PotatoesMar 28–Apr 11
OnionsMar 14–Apr 4
CarrotsApr 4–May 9
LettuceApr 11–May 2
BroccoliMar 28–Apr 11
BeetsMar 28–May 9
PeasMar 14–Mar 28
CabbageMar 28–Apr 11
RadishesMar 21–May 2
Brussels sproutsApr 11–Apr 25
SpinachMar 14–Apr 4
CilantroApr 11–May 2
KaleMar 28–Apr 11
Collard greensMar 28–Apr 11
TurnipsMar 28–Apr 11
DillApr 25–May 9
CeleryMay 2–May 9
CauliflowerApr 11–Apr 25
LeeksApr 11–Apr 25
Swiss chardApr 11–May 9
ParsleyApr 11–May 2
Tulip bulbsOct 10–Nov 14
GarlicOct 3–Nov 7
Daffodil bulbsSep 26–Nov 7
StrawberriesMar 28–Apr 11
AsparagusMar 28–Apr 11Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 10 | Apr 25 | May 12 | Oct 8 | Oct 24 | Nov 5 |
| Hard freeze, 28°F | Mar 29 | Apr 10 | Apr 25 | Oct 20 | Nov 4 | Nov 18 |
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 Williamsport 2 (USC00369735) sits 2.8 miles from the center of Williamsport at 525 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 Williamsport, PA?
The average last frost date in Williamsport is April 25, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 12.
When is the first frost in Williamsport?
The first frost in fall usually comes around October 24. One year in ten it arrives before October 8.
How long is the growing season in Williamsport?
About 181 days between the average last and first frost.
When should I plant tomatoes in Williamsport?
Plant tomato seedlings outside from May 2 to May 16. Start seeds indoors six to eight weeks earlier.
Nearby in Pennsylvania
- State CollegeApr 20
- HazletonApr 30
- Wilkes-BarreApr 23
- HarrisburgApr 15
- LebanonApr 20
- ScrantonApr 23
- CarlisleApr 23
- ReadingApr 14
- AltoonaApr 25
- YorkApr 26
- LancasterApr 19
- AllentownApr 20