Frost dates for Portal, 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
May 3
typical year
Safe to plant
May 16
frost is over in 9 of 10 years
First fall frost
October 25
typical year
Growing season
174 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 | – | Apr 5 – 19 | – |
| Spinach | – | Mar 22 – Apr 12 | Aug 30 – Sep 13 |
| Lettuce | – | Apr 5 – 26 | Aug 30 – Sep 13 |
| Radishes | – | Apr 5 – May 17 | Sep 13 – 27 |
| Onions | – | Apr 5 – 19 | – |
| Potatoes | – | Apr 12 – 26 | – |
| Carrots | – | Apr 12 – May 3 | Aug 2 – 16 |
| Beets | – | Apr 5 – 19 | Aug 16 – 30 |
| Kale | Feb 22 – Mar 8 | Apr 5 – 19 | Aug 16 – 30 |
| Broccoli | Feb 22 – Mar 8 | Apr 19 – May 3 | Aug 16 – 30 |
| Cabbage | Feb 8 – 22 | Apr 5 – 19 | Aug 16 – 30 |
| Garlic | – | – | Sep 13 – Oct 4 |
| Warm-season crops | |||
| Tomatoes | Mar 21 – Apr 4 | May 16 – 30 | – |
| Peppers | Mar 14 – 28 | May 23 – Jun 6 | – |
| Cucumbers | – | May 16 – Jun 6 | – |
| Zucchini | – | May 16 – Jun 13 | – |
| Pumpkins | – | May 16 – Jun 6 | – |
| Green beans | – | May 16 – Aug 16 | – |
| Sweet corn | – | May 16 – Jun 13 | – |
| Basil | Apr 11 – 25 | May 23 – 30 | – |
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 | May 16 | May 3 | April 16 |
| Fall frost before | October 11 | October 25 | November 6 |
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 April 16 (May 5 in a late year), and the first one in fall around November 4.
Where these dates come from
NOAA weather station PORTAL 4 SW, AZ US (USC00026716), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 12 miles:
88056
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.