Frost dates for Mormon Flat, AZ
At Mormon Flat, the median last spring frost (32°F) is Jan 29 and the median first fall frost is Dec 24, for a typical growing season of 334 days. For a 90% chance that the last frost has passed, wait until Feb 23. Nearby ZIP codes are in USDA hardiness zone 9b.
- Jan 29Last spring frost (median)50% chance of 32°F after this date
- Feb 23Safer planting date10% chance of 32°F after this date
- Dec 24First fall frost (median)50% chance of 32°F by this date
- 334 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Jan 21 | Feb 19 | Mar 12 |
| 32°F | Dec 23 | Jan 29 | Feb 23 |
| 28°F | Dec 14 | Jan 10 | Feb 7 |
| 24°F | Dec 21 | Jan 5 | Jan 26 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Nov 22 | Dec 11 | Dec 29 |
| 32°F | Dec 3 | Dec 24 | Jan 28 |
| 28°F | Dec 13 | Jan 2 | Feb 4 |
| 24°F | Dec 21 | Jan 3 | Jan 25 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 264 days | 294 days | 328 days |
| 32°F | 302 days | 334 days | 365 days |
| 28°F | 334 days | 365 days | 365 days |
| 24°F | 362 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 87% |
| 28°F | 37% |
| 24°F | 10% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 85215 | 9b | 25 to 30°F | 14 km |
| 85264 | 9b | 25 to 30°F | 15 km |
| 85119 | 9b | 25 to 30°F | 20 km |
| 85207 | 9b | 25 to 30°F | 21 km |
| 85120 | 9b | 25 to 30°F | 22 km |
| 85118 | 9b | 25 to 30°F | 23 km |
| 85208 | 9b | 25 to 30°F | 24 km |
| 85209 | 9b | 25 to 30°F | 26 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00025700, at 33.5544, -111.4425, elevation 520 m (1,705 ft).
- Data quality: Estimated from nearby stations (2+ years), 3 years of freeze data.
- Average days per year at or below 32°F: 3.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Stewart Mountain Dam (9 km)
- Apache Junction 5 NE (11 km)
- E Mesa (24 km)
- Fountain Hills (26 km)
- Roosevelt 1 S (33 km)
- Punkin Center (36 km)
- Superior (43 km)
- Pinnacle Peak (43 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.