Last spring frost
Mar 25
Frost Dates for Swift Trail Junction, AZ
First fall frost
Nov 9
Growing season
228 days
Hardiness zone
8b
In an average year around Swift Trail Junction, AZ, the last spring frost (32°F) is about Mar 25 and the first fall frost is about Nov 9, giving roughly a 228-day growing season. To be safe most years, wait until Mar 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) | May 2 | Apr 12 | Mar 25 |
| Freeze (32°F) | Apr 14 | Mar 25 | Mar 5 |
| Hard (28°F) | Mar 23 | Mar 3 | Feb 8 |
| Severe (24°F) | Mar 6 | Feb 11 | Jan 15 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 2 | Apr 25 | Apr 20 | Apr 17 | Apr 12 | Apr 9 | Apr 6 | Apr 1 | Mar 25 |
| 32°F | Apr 14 | Apr 7 | Apr 3 | Mar 30 | Mar 25 | Mar 20 | Mar 15 | Mar 10 | Mar 5 |
| 28°F | Mar 23 | Mar 15 | Mar 10 | Mar 6 | Mar 3 | Feb 28 | Feb 22 | Feb 16 | Feb 8 |
| 24°F | Mar 6 | Feb 28 | Feb 23 | Feb 16 | Feb 11 | Feb 7 | Feb 2 | Jan 29 | Jan 15 |
| 20°F | Feb 18 | Feb 8 | Feb 3 | Jan 30 | Jan 23 | Jan 16 | Jan 9 | Dec 31 | Dec 20 |
| 16°F | Feb 9 | Feb 1 | Jan 24 | Jan 17 | Jan 11 | Jan 6 | Dec 31 | Dec 22 | Dec 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) | Oct 14 | Oct 30 | Nov 13 |
| Freeze (32°F) | Oct 23 | Nov 9 | Nov 25 |
| Hard (28°F) | Nov 3 | Nov 22 | Dec 6 |
| Severe (24°F) | Nov 16 | Dec 3 | Dec 23 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 14 | Oct 18 | Oct 23 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 13 |
| 32°F | Oct 23 | Oct 30 | Nov 3 | Nov 6 | Nov 9 | Nov 13 | Nov 16 | Nov 20 | Nov 25 |
| 28°F | Nov 3 | Nov 10 | Nov 15 | Nov 18 | Nov 22 | Nov 24 | Nov 28 | Dec 1 | Dec 6 |
| 24°F | Nov 16 | Nov 22 | Nov 26 | Nov 30 | Dec 3 | Dec 6 | Dec 11 | Dec 15 | Dec 23 |
| 20°F | Nov 28 | Dec 4 | Dec 9 | Dec 15 | Dec 20 | Dec 24 | Dec 29 | Jan 4 | Jan 16 |
| 16°F | Dec 6 | Dec 14 | Dec 22 | Dec 28 | Jan 1 | Jan 6 | Jan 12 | Jan 20 | Feb 1 |
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: Safford Ag Ctr, Az, about 9.6 miles away@if(!empty($station['elevation_ft'])), at 2,954 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 Swift Trail Junction, AZ?
On average, the last spring frost (32°F) around Swift Trail Junction, AZ is about Mar 25. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 5.
When is the first frost in the fall?
The first fall frost around Swift Trail Junction, AZ typically arrives about Nov 9. 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 25 on average, or Mar 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 228 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 85546 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026