Last spring frost
Feb 1
Frost Dates for San Tan Valley, AZ
First fall frost
Dec 11
Growing season
315 days
Hardiness zone
9b
In an average year around San Tan Valley, AZ, the last spring frost (32°F) is about Feb 1 and the first fall frost is about Dec 11, giving roughly a 315-day growing season. To be safe most years, wait until Jan 2 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) | Mar 11 | Feb 21 | Jan 29 |
| Freeze (32°F) | Feb 27 | Feb 1 | Jan 2 |
| Hard (28°F) | Feb 11 | Jan 8 | Dec 15 |
| Severe (24°F) | Jan 29 | Jan 2 | Dec 13 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 11 | Mar 6 | Mar 2 | Feb 26 | Feb 21 | Feb 16 | Feb 11 | Feb 5 | Jan 29 |
| 32°F | Feb 27 | Feb 18 | Feb 12 | Feb 5 | Feb 1 | Jan 24 | Jan 17 | Jan 8 | Jan 2 |
| 28°F | Feb 11 | Feb 2 | Jan 24 | Jan 15 | Jan 8 | Jan 3 | Dec 31 | Dec 24 | Dec 15 |
| 24°F | Jan 29 | Jan 18 | Jan 9 | Jan 5 | Jan 2 | Jan 1 | Dec 30 | Dec 23 | Dec 13 |
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) | Nov 12 | Nov 28 | Dec 14 |
| Freeze (32°F) | Nov 23 | Dec 11 | Jan 1 |
| Hard (28°F) | Dec 4 | Dec 26 | Jan 29 |
| Severe (24°F) | Dec 13 | Jan 1 | Jan 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 12 | Nov 18 | Nov 22 | Nov 25 | Nov 28 | Dec 1 | Dec 5 | Dec 9 | Dec 14 |
| 32°F | Nov 23 | Nov 29 | Dec 3 | Dec 7 | Dec 11 | Dec 15 | Dec 19 | Dec 25 | Jan 1 |
| 28°F | Dec 4 | Dec 11 | Dec 16 | Dec 21 | Dec 26 | Dec 30 | Jan 2 | Jan 12 | Jan 29 |
| 24°F | Dec 13 | Dec 19 | Dec 27 | Dec 30 | Jan 1 | Jan 2 | Jan 6 | Jan 13 | Jan 24 |
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: Chandler Heights, Az, about 10 miles away@if(!empty($station['elevation_ft'])), at 1,425 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 San Tan Valley, AZ?
On average, the last spring frost (32°F) around San Tan Valley, AZ is about Feb 1. In cooler years it can run later, so for a safer bet many gardeners wait until Jan 2.
When is the first frost in the fall?
The first fall frost around San Tan Valley, AZ typically arrives about Dec 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 Feb 1 on average, or Jan 2 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 315 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 85143 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026