Last frost date in Flagstaff, AZ
The average last frost in Flagstaff is June 4. By June 19 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about September 28, which leaves 115 frost-free days. An early freeze before September 16 happens one year in ten.
- Safe after (10% risk)
- Jun 19
- Average first frost
- Sep 28
- Frost-free season
- 115 days
- Hard freeze (28°F) ends
- May 20
Frost possible in low spots Fri night, low 36°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2239°
- FriOct 2336°possible frost
- SatOct 2434°possible frost
- SunOct 2535°possible frost
- MonOct 2636°possible frost
- TueOct 2737°
Planting calendar for Flagstaff
Windows count forward or back from the average frost dates above. Click a crop for dates across Arizona.
TomatoesJun 11–Jun 25
PumpkinsJun 18–Jul 2
SunflowersJun 4–Jun 25
CucumbersJun 18–Jun 25
CornJun 11–Jun 25
Sweet potatoesJun 25–Jul 9
WatermelonJun 18–Jul 2
Green beansJun 11–Jul 2
ZucchiniJun 11–Jun 25
OkraJun 25–Jul 9
PeppersJun 18–Jul 2
BasilJun 11–Jun 25
Butternut squashJun 11–Jun 25
CantaloupeJun 18–Jul 2
EggplantJun 18–Jul 2
PotatoesMay 7–May 21
OnionsApr 23–May 14
CarrotsMay 14–Jun 18
LettuceMay 21–Jun 11
BroccoliMay 7–May 21
BeetsMay 7–Jun 18
PeasApr 23–May 7
CabbageMay 7–May 21
RadishesApr 30–Jun 11
Brussels sproutsMay 21–Jun 4
SpinachApr 23–May 14
CilantroMay 21–Jun 11
KaleMay 7–May 21
Collard greensMay 7–May 21
TurnipsMay 7–May 21
DillJun 4–Jun 18
CeleryJun 11–Jun 18
CauliflowerMay 21–Jun 4
LeeksMay 21–Jun 4
Swiss chardMay 21–Jun 18
ParsleyMay 21–Jun 11
Tulip bulbsSep 14–Oct 19
GarlicSep 7–Oct 12
Daffodil bulbsAug 31–Oct 12
StrawberriesMay 7–May 21
AsparagusMay 7–May 21The frost-free season here is short for pumpkins, sweet potatoes, butternut squash. Start them indoors and look for early varieties.
Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | May 21 | Jun 4 | Jun 19 | Sep 16 | Sep 28 | Oct 9 |
| Hard freeze, 28°F | May 1 | May 20 | Jun 6 | Sep 28 | Oct 9 | Oct 22 |
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 Flagstaff Pulliam Airport (USW00003103) sits 3.8 miles from the center of Flagstaff at 7,003 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 Flagstaff, AZ?
The average last frost date in Flagstaff is June 4, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after June 19.
When is the first frost in Flagstaff?
The first frost in fall usually comes around September 28. One year in ten it arrives before September 16.
How long is the growing season in Flagstaff?
About 115 days between the average last and first frost.
When should I plant tomatoes in Flagstaff?
Plant tomato seedlings outside from June 11 to June 25. Start seeds indoors six to eight weeks earlier.
Nearby in Arizona
- Prescott ValleyApr 30
- PrescottApr 30
- ScottsdaleJan 27
- PhoenixJan 8
- Sun CityJan 20
- El MirageJan 20
- GlendaleJan 20
- TempeFeb 13
- GilbertFeb 1
- ChandlerFeb 13
- Queen CreekFeb 1
- KingmanApr 2