Last spring frost
Mar 16
Frost Dates for Whetstone, AZ
First fall frost
Nov 21
Growing season
246 days
Hardiness zone
8b
In an average year around Whetstone, AZ, the last spring frost (32°F) is about Mar 16 and the first fall frost is about Nov 21, giving roughly a 246-day growing season. To be safe most years, wait until Feb 19 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) | Apr 26 | Apr 9 | Mar 20 |
| Freeze (32°F) | Apr 12 | Mar 16 | Feb 19 |
| Hard (28°F) | Mar 23 | Feb 20 | Jan 16 |
| Severe (24°F) | Feb 23 | Jan 26 | Dec 23 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 26 | Apr 22 | Apr 17 | Apr 12 | Apr 9 | Apr 6 | Apr 1 | Mar 27 | Mar 20 |
| 32°F | Apr 12 | Apr 6 | Mar 31 | Mar 23 | Mar 16 | Mar 12 | Mar 7 | Mar 1 | Feb 19 |
| 28°F | Mar 23 | Mar 9 | Mar 3 | Feb 27 | Feb 20 | Feb 13 | Feb 7 | Jan 30 | Jan 16 |
| 24°F | Feb 23 | Feb 14 | Feb 8 | Feb 1 | Jan 26 | Jan 16 | Jan 9 | Jan 3 | Dec 23 |
| 20°F | Feb 14 | Feb 7 | Jan 29 | Jan 19 | Jan 9 | Jan 5 | Dec 31 | Dec 25 | Dec 15 |
| 16°F | Feb 16 | Feb 12 | Feb 9 | Feb 1 | Jan 20 | Jan 9 | Jan 4 | Jan 1 | Dec 27 |
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) | Oct 24 | Nov 8 | Nov 24 |
| Freeze (32°F) | Nov 3 | Nov 21 | Dec 7 |
| Hard (28°F) | Nov 18 | Dec 6 | Dec 24 |
| Severe (24°F) | Dec 1 | Dec 22 | Jan 25 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 24 | Oct 29 | Nov 1 | Nov 5 | Nov 8 | Nov 12 | Nov 16 | Nov 19 | Nov 24 |
| 32°F | Nov 3 | Nov 8 | Nov 14 | Nov 18 | Nov 21 | Nov 24 | Nov 29 | Dec 3 | Dec 7 |
| 28°F | Nov 18 | Nov 25 | Nov 29 | Dec 3 | Dec 6 | Dec 9 | Dec 13 | Dec 17 | Dec 24 |
| 24°F | Dec 1 | Dec 7 | Dec 11 | Dec 16 | Dec 22 | Dec 26 | Jan 1 | Jan 10 | Jan 25 |
| 20°F | Dec 10 | Dec 18 | Dec 24 | Dec 29 | Jan 1 | Jan 7 | Jan 15 | Jan 28 | Feb 7 |
| 16°F | Dec 27 | Jan 1 | Jan 4 | Jan 6 | Jan 16 | Jan 28 | Feb 6 | Feb 11 | Feb 15 |
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: Ft Huachuca Pioneer Airfield, Az, about 9 miles away@if(!empty($station['elevation_ft'])), at 4,768 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 Whetstone, AZ?
On average, the last spring frost (32°F) around Whetstone, AZ is about Mar 16. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 19.
When is the first frost in the fall?
The first fall frost around Whetstone, AZ typically arrives about Nov 21. 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 Mar 16 on average, or Feb 19 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 246 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 85616 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026