Frost dates for Flagstaff, AZ
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
June 4
typical year
Safe to plant
June 19
frost is over in 9 of 10 years
First fall frost
September 28
typical year
Growing season
115 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | May 7 – 21 | – |
| Spinach | – | Apr 23 – May 14 | Aug 3 – 17 |
| Lettuce | – | May 7 – 28 | Aug 3 – 17 |
| Radishes | – | May 7 – Jun 18 | Aug 17 – 31 |
| Onions | – | May 7 – 21 | – |
| Potatoes | – | May 14 – 28 | – |
| Carrots | – | May 14 – Jun 4 | Jul 6 – 20 |
| Beets | – | May 7 – 21 | Jul 20 – Aug 3 |
| Kale | Mar 26 – Apr 9 | May 7 – 21 | Jul 20 – Aug 3 |
| Broccoli | Mar 26 – Apr 9 | May 21 – Jun 4 | Jul 20 – Aug 3 |
| Cabbage | Mar 12 – 26 | May 7 – 21 | Jul 20 – Aug 3 |
| Garlic | – | – | Aug 17 – Sep 7 |
| Warm-season crops | |||
| Tomatoes | Apr 24 – May 8 | Jun 19 – Jul 3 | – |
| Peppers | Apr 17 – May 1 | Jun 26 – Jul 10 | – |
| Cucumbers | – | Jun 19 – Jul 10 | – |
| Zucchini | – | Jun 19 – Jul 17 | – |
| Pumpkins | – | Jun 19 – Jul 10 | – |
| Green beans | – | Jun 19 – Jul 20 | – |
| Sweet corn | – | Jun 19 – Jul 17 | – |
| Basil | May 15 – 29 | Jun 26 – Jul 3 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | June 19 | June 4 | May 21 |
| Fall frost before | September 16 | September 28 | October 9 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around May 20 (June 6 in a late year), and the first one in fall around October 9.
Towns that use these dates
This is the nearest NOAA station with frost records for 1 town.
Flagstaff
Where these dates come from
NOAA weather station FLAGSTAFF PULLIAM AP, AZ US (USW00003103), 1991–2020 climate normals. It's the nearest station for 2 zip codes, all within 5 miles:
86005, 86011
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.