Last spring frost
May 20
Frost Dates for Vernon, AZ
First fall frost
Oct 11
Growing season
142 days
Hardiness zone
6b
In an average year around Vernon, AZ, the last spring frost (32°F) is about May 20 and the first fall frost is about Oct 11, giving roughly a 142-day growing season. To be safe most years, wait until May 5 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 12 | Jun 1 | May 19 |
| Freeze (32°F) | Jun 4 | May 20 | May 5 |
| Hard (28°F) | May 23 | May 6 | Apr 22 |
| Severe (24°F) | May 10 | Apr 23 | Apr 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 12 | Jun 8 | Jun 5 | Jun 3 | Jun 1 | May 30 | May 26 | May 22 | May 19 |
| 32°F | Jun 4 | May 31 | May 26 | May 23 | May 20 | May 17 | May 14 | May 9 | May 5 |
| 28°F | May 23 | May 16 | May 13 | May 9 | May 6 | May 3 | May 1 | Apr 28 | Apr 22 |
| 24°F | May 10 | May 4 | Apr 30 | Apr 26 | Apr 23 | Apr 19 | Apr 15 | Apr 11 | Apr 5 |
| 20°F | Apr 26 | Apr 17 | Apr 12 | Apr 8 | Apr 4 | Mar 31 | Mar 26 | Mar 17 | Mar 10 |
| 16°F | Apr 6 | Mar 30 | Mar 20 | Mar 13 | Mar 9 | Mar 5 | Feb 28 | Feb 21 | Feb 12 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 21 | Oct 2 | Oct 14 |
| Freeze (32°F) | Sep 29 | Oct 11 | Oct 24 |
| Hard (28°F) | Oct 7 | Oct 22 | Nov 6 |
| Severe (24°F) | Oct 17 | Nov 2 | Nov 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 21 | Sep 25 | Sep 28 | Oct 1 | Oct 2 | Oct 5 | Oct 7 | Oct 11 | Oct 14 |
| 32°F | Sep 29 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 24 |
| 28°F | Oct 7 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 24 | Oct 28 | Nov 1 | Nov 6 |
| 24°F | Oct 17 | Oct 21 | Oct 26 | Oct 30 | Nov 2 | Nov 5 | Nov 9 | Nov 15 | Nov 20 |
| 20°F | Oct 25 | Nov 1 | Nov 6 | Nov 10 | Nov 14 | Nov 17 | Nov 21 | Nov 24 | Nov 29 |
| 16°F | Nov 4 | Nov 10 | Nov 16 | Nov 19 | Nov 23 | Nov 26 | Nov 30 | Dec 5 | Dec 11 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Mc Nary 2N, Az, about 13.1 miles away@if(!empty($station['elevation_ft'])), at 7,340 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Vernon, AZ?
On average, the last spring frost (32°F) around Vernon, AZ is about May 20. In cooler years it can run later, so for a safer bet many gardeners wait until May 5.
When is the first frost in the fall?
The first fall frost around Vernon, AZ typically arrives about Oct 11. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 20 on average, or May 5 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 142 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 85940 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026