Last spring frost
Mar 26
Frost Dates for Dewey-Humboldt, AZ
First fall frost
Nov 25
Growing season
242 days
Hardiness zone
8a
In an average year around Dewey-Humboldt, AZ, the last spring frost (32°F) is about Mar 26 and the first fall frost is about Nov 25, giving roughly a 242-day growing season. To be safe most years, wait until Feb 28 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) | May 5 | Apr 13 | Mar 21 |
| Freeze (32°F) | Apr 19 | Mar 26 | Feb 28 |
| Hard (28°F) | Apr 4 | Mar 1 | Jan 27 |
| Severe (24°F) | Mar 6 | Jan 31 | Dec 27 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 5 | Apr 29 | Apr 23 | Apr 18 | Apr 13 | Apr 9 | Apr 5 | Mar 31 | Mar 21 |
| 32°F | Apr 19 | Apr 10 | Apr 5 | Mar 31 | Mar 26 | Mar 20 | Mar 15 | Mar 8 | Feb 28 |
| 28°F | Apr 4 | Mar 22 | Mar 13 | Mar 7 | Mar 1 | Feb 23 | Feb 16 | Feb 7 | Jan 27 |
| 24°F | Mar 6 | Feb 24 | Feb 14 | Feb 7 | Jan 31 | Jan 22 | Jan 12 | Jan 4 | Dec 27 |
| 20°F | Feb 15 | Feb 6 | Jan 30 | Jan 21 | Jan 13 | Jan 6 | Jan 3 | Dec 29 | Dec 18 |
| 16°F | Feb 11 | Feb 4 | Jan 28 | Jan 18 | Jan 9 | Jan 5 | Jan 2 | Dec 31 | Dec 22 |
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 12 | Nov 29 |
| Freeze (32°F) | Nov 4 | Nov 25 | Dec 10 |
| Hard (28°F) | Nov 17 | Dec 6 | Dec 26 |
| Severe (24°F) | Nov 26 | Dec 21 | Jan 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 24 | Oct 30 | Nov 3 | Nov 7 | Nov 12 | Nov 16 | Nov 20 | Nov 24 | Nov 29 |
| 32°F | Nov 4 | Nov 12 | Nov 17 | Nov 21 | Nov 25 | Nov 28 | Dec 1 | Dec 6 | Dec 10 |
| 28°F | Nov 17 | Nov 24 | Nov 28 | Dec 1 | Dec 6 | Dec 9 | Dec 14 | Dec 18 | Dec 26 |
| 24°F | Nov 26 | Dec 3 | Dec 10 | Dec 16 | Dec 21 | Dec 25 | Dec 30 | Jan 5 | Jan 24 |
| 20°F | Dec 8 | Dec 18 | Dec 24 | Dec 29 | Jan 1 | Jan 6 | Jan 15 | Jan 26 | Feb 5 |
| 16°F | Dec 20 | Dec 28 | Jan 1 | Jan 4 | Jan 7 | Jan 13 | Jan 25 | Feb 2 | Feb 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: Jerome, Az, about 13.5 miles away@if(!empty($station['elevation_ft'])), at 4,950 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 Dewey-Humboldt, AZ?
On average, the last spring frost (32°F) around Dewey-Humboldt, AZ is about Mar 26. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 28.
When is the first frost in the fall?
The first fall frost around Dewey-Humboldt, AZ typically arrives about Nov 25. 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 26 on average, or Feb 28 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 242 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 86327 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026