Fountain Hills, AZ planting calendar
- USDA zone
- 9b25 to 30 °F
- Last frost
- Jan 6avg, 32°F
- First frost
- Dec 28avg, 32°F
- Growing season
- 356days
Fountain Hills, Arizona is in USDA plant hardiness zone 9b. Its average last spring frost is around January 6 and the first fall frost around December 28, giving a growing season of about 356 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Fountain Hills planting calendar
Each crop's windows are counted from Fountain Hills's average frost dates. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Jan 1 | Jan 13 – Jan 20 | Mar 14 – Apr 3 | — |
| Pepper | Very tender | Jan 1 | Jan 20 – Jan 27 | Mar 21 – Apr 20 | — |
| Cucumber | Tender | Jan 1 | Jan 13 – Jan 20 | Mar 4 – Mar 24 | — |
| Summer squash / zucchini | Tender | — | Jan 13 – Jan 20 | Feb 27 – Mar 14 | — |
| Bush bean | Tender | — | Jan 13 – Jan 20 | Mar 4 – Mar 14 | Oct 29 – Nov 8 |
| Sweet corn | Tender | — | Jan 6 – Jan 20 | Mar 7 – Apr 6 | — |
| Basil | Very tender | Jan 1 | Jan 13 – Jan 20 | Feb 12 – Feb 27 | — |
| Lettuce | Half-hardy | Jan 1 | Jan 1 | Feb 15 – Mar 2 | Oct 15 – Oct 30 |
| Pea | Hardy | — | Jan 1 | Feb 25 – Mar 12 | Oct 5 – Oct 20 |
| Spinach | Hardy | — | Jan 1 | Feb 10 – Feb 20 | Oct 25 – Nov 4 |
| Carrot | Half-hardy | — | Jan 1 | Mar 2 – Mar 22 | Sep 25 – Oct 15 |
| Broccoli | Half-hardy | Jan 1 | Jan 1 | Feb 25 – Mar 17 | Sep 30 – Oct 20 |
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USC00023190. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 (p10 for spring, p90 for fall) — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Jan 31 | Mar 1 | Dec 14 | Jan 3 | 317 |
| 32°F (freeze) | Jan 6 | Feb 11 | Dec 28 | Jan 27 | 356 |
| 28°F | Jan 9 | Jan 31 | Jan 8 | Jan 31 | 365 |
| 24°F | — | — | — | — | 365 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 8,179 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 11,755 | cool-season crops (brassicas, greens) |
Hardiness zone 9b
Fountain Hills sits in USDA plant hardiness zone 9b on the 2023 map — meaning its average annual extreme minimum winter temperature is about 25 to 30 °F. That number tells you which perennials, shrubs, and trees reliably survive an average winter here; it does not set your planting dates, which come from the frost calendar above.
Explore more places in zone 9b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Fountain Hills?
- Fountain Hills, Arizona is in USDA plant hardiness zone 9b on the 2023 map (average annual extreme minimum temperature 25 to 30 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Fountain Hills?
- The average (median) last spring frost at 32°F is around January 6, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as February 11, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Fountain Hills?
- The average first fall frost at 32°F is around December 28. That leaves a growing season of about 356 days between the average last spring and first fall frosts.
- When should I start tomatoes in Fountain Hills?
- Start tomato seeds indoors about Jan 1 and transplant them outside about Jan 13 – Jan 20, once the danger of frost has passed. Estimated first harvest is around Mar 14 – Apr 3.
- How long is the growing season in Fountain Hills?
- About 356 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~January 6) and the average first fall frost (~December 28). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USC00023190 (Fountain Hills, 2.3 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.