Last spring frost
Jun 10
Frost Dates for Mormon Lake, AZ
First fall frost
Sep 27
Growing season
106 days
Hardiness zone
6b
In an average year around Mormon Lake, AZ, the last spring frost (32°F) is about Jun 10 and the first fall frost is about Sep 27, giving roughly a 106-day growing season. To be safe most years, wait until May 26 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) | Jul 8 | Jun 24 | Jun 11 |
| Freeze (32°F) | Jun 27 | Jun 10 | May 26 |
| Hard (28°F) | Jun 12 | May 26 | May 5 |
| Severe (24°F) | May 26 | May 3 | Apr 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 8 | Jul 2 | Jun 30 | Jun 28 | Jun 24 | Jun 21 | Jun 18 | Jun 14 | Jun 11 |
| 32°F | Jun 27 | Jun 21 | Jun 17 | Jun 14 | Jun 10 | Jun 8 | Jun 5 | Jun 2 | May 26 |
| 28°F | Jun 12 | Jun 6 | Jun 3 | May 31 | May 26 | May 21 | May 17 | May 12 | May 5 |
| 24°F | May 26 | May 17 | May 12 | May 7 | May 3 | Apr 30 | Apr 27 | Apr 23 | Apr 18 |
| 20°F | May 2 | Apr 27 | Apr 22 | Apr 19 | Apr 14 | Apr 11 | Apr 7 | Apr 3 | Mar 29 |
| 16°F | Apr 13 | Apr 7 | Apr 3 | Mar 30 | Mar 24 | Mar 18 | Mar 14 | Mar 8 | Mar 3 |
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 5 | Sep 17 | Sep 27 |
| Freeze (32°F) | Sep 14 | Sep 27 | Oct 8 |
| Hard (28°F) | Sep 26 | Oct 7 | Oct 22 |
| Severe (24°F) | Oct 6 | Oct 20 | Nov 4 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 5 | Sep 8 | Sep 12 | Sep 14 | Sep 17 | Sep 19 | Sep 22 | Sep 24 | Sep 27 |
| 32°F | Sep 14 | Sep 19 | Sep 22 | Sep 25 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 8 |
| 28°F | Sep 26 | Sep 30 | Oct 2 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 22 |
| 24°F | Oct 6 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 23 | Oct 27 | Nov 1 | Nov 4 |
| 20°F | Oct 17 | Oct 22 | Oct 26 | Oct 29 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 16 |
| 16°F | Oct 27 | Nov 1 | Nov 6 | Nov 10 | Nov 14 | Nov 17 | Nov 21 | Nov 24 | Nov 30 |
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: Mund's Park, Az, about 8.7 miles away@if(!empty($station['elevation_ft'])), at 6,470 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 Mormon Lake, AZ?
On average, the last spring frost (32°F) around Mormon Lake, AZ is about Jun 10. In cooler years it can run later, so for a safer bet many gardeners wait until May 26.
When is the first frost in the fall?
The first fall frost around Mormon Lake, AZ typically arrives about Sep 27. 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 Jun 10 on average, or May 26 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 106 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 86038 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026