Frost dates for Stewart Mountain Dam, AZ
At Stewart Mountain Dam, the median last spring frost (32°F) is Feb 13 and the median first fall frost is Dec 5, for a typical growing season of 295 days. For a 90% chance that the last frost has passed, wait until Mar 8. Nearby ZIP codes are in USDA hardiness zone 9b.
- Feb 13Last spring frost (median)50% chance of 32°F after this date
- Mar 8Safer planting date10% chance of 32°F after this date
- Dec 5First fall frost (median)50% chance of 32°F by this date
- 295 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 | Feb 8 | Mar 3 | Apr 3 |
| 32°F | Jan 10 | Feb 13 | Mar 8 |
| 28°F | Dec 18 | Jan 18 | Feb 20 |
| 24°F | Dec 13 | Jan 5 | Feb 1 |
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 7 | Nov 23 | Dec 9 |
| 32°F | Nov 18 | Dec 5 | Dec 26 |
| 28°F | Nov 28 | Dec 19 | Jan 21 |
| 24°F | Dec 6 | Jan 1 | 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 | 223 days | 260 days | 288 days |
| 32°F | 262 days | 295 days | 330 days |
| 28°F | 301 days | 336 days | 365 days |
| 24°F | 340 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 84% |
| 24°F | 32% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 85215 | 9b | 25 to 30°F | 6 km |
| 85264 | 9b | 25 to 30°F | 15 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 USC00028214, at 33.5575, -111.5358, elevation 433 m (1,422 ft).
- Data quality: Representative (10+ years), 14 years of freeze data.
- Average days per year at or below 32°F: 17.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Mormon Flat (9 km)
- Apache Junction 5 NE (12 km)
- Fountain Hills (17 km)
- E Mesa (18 km)
- Scottsdale Muni Airport (35 km)
- Pinnacle Peak (36 km)
- Tempe Asu (39 km)
- Punkin Center (39 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.