Frost Dates & Planting Calendar for Flagstaff, AZ
Plan your garden around Flagstaff, AZ's typical frost-free growing season, using NOAA climate normals and a 42-crop planting calendar built for this location.
Last Spring Frost
June 4
Safe Jun 19
Typical Jun 4
Risky May 21
First Fall Frost
September 28
Safe Sep 16
Typical Sep 28
Risky Oct 9
Growing Season
115 days
Typical last frost to typical first frost.
USDA Hardiness Zone
Zone 6a
A classic four-season climate with cold winters and a solid summer growing season.
Data: NOAA station FLAGSTAFF PULLIAM AP, AZ US, 6.1 km away.
—
days until the typical last spring frost
Monthly Temperatures
Avg. high
Avg. temp
Avg. low
Planting Calendar
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Tomato | Apr 9 – Apr 23 | — | Jun 11 – Jun 18 | — | 60–85 days | Start indoors 6-8 weeks before last frost; transplant out 1-2 weeks after last frost once soil has warmed. |
| Pepper | Mar 26 – Apr 9 | — | Jun 11 – Jun 25 | — | 60–90 days | Slow to germinate; start indoors 8-10 weeks before last frost. Transplant only once nights stay above 55F, 1-3 weeks after last frost. |
| Eggplant | Mar 26 – Apr 9 | — | Jun 18 – Jun 25 | — | 65–85 days | Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant. |
| Cucumber | May 7 – May 14 | Jun 11 – Jun 18 | Jun 11 – Jun 18 | — | 50–65 days | Can be started indoors 3-4 weeks before transplanting, or direct-sown 1-2 weeks after last frost once soil is warm. |
| Zucchini | May 14 – May 21 | Jun 11 – Jun 25 | Jun 11 – Jun 18 | — | 45–55 days | Fast-growing squash; direct sow 1-3 weeks after last frost, or start indoors 2-3 weeks early for a head start. |
| Winter Squash | May 7 – May 14 | Jun 11 – Jun 25 | Jun 11 – Jun 18 | — | 80–110 days | Long season; direct sow after soil warms, or start indoors 3-4 weeks before last frost in short-season climates. |
| Pumpkin | — | Jun 11 – Jun 25 | — | — | 90–120 days | Direct sow 1-3 weeks after last frost; back-time from your first fall frost so the 90-120 day maturity window lands before it. |
| Watermelon | May 7 – May 14 | — | Jun 18 – Jun 25 | — | 70–90 days | Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost. |
| Cantaloupe | May 7 – May 14 | — | Jun 18 – Jun 25 | — | 70–90 days | Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting. |
| Corn | — | Jun 4 – Jun 18 | — | — | 60–100 days | Direct sow at last frost to 2 weeks after, once soil reaches 60F; does not transplant well. Succession sow every 2 weeks. |
| Green Bean | — | Jun 4 – Jun 18 | — | — | 50–65 days | Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush. |
| Pea | — | Apr 23 – May 7 | — | — | 55–70 days | Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Lettuce | — | May 7 – May 21 | — | Aug 3 – Aug 17 | 45–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts. |
| Spinach | — | Apr 23 – May 7 | — | Aug 3 – Aug 17 | 40–50 days | Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked. |
| Kale | — | May 7 – May 21 | — | Jul 20 – Aug 3 | 50–65 days | Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants. |
| Arugula | — | May 7 – May 21 | — | Aug 17 – Aug 24 | 30–40 days | Fast-growing, cold-tolerant green; direct sow 2-4 weeks before last frost, succession sow every 2-3 weeks. |
| Swiss Chard | — | May 14 – May 28 | — | — | 50–60 days | Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too. |
| Broccoli | Apr 16 – Apr 30 | — | May 14 – May 21 | Jul 27 – Aug 3 | 55–80 days | Start indoors 5-7 weeks before last frost; transplant out 2-3 weeks before last frost (hardens off to light frost). |
| Cauliflower | Apr 16 – Apr 30 | — | May 21 – May 28 | Jul 20 – Jul 27 | 55–85 days | Fussier than broccoli about temperature swings; start indoors 5-7 weeks before last frost, transplant 1-2 weeks before last frost. |
| Cabbage | Apr 16 – Apr 30 | — | May 7 – May 21 | Jul 20 – Aug 3 | 60–100 days | Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost. |
| Brussels Sprouts | Apr 16 – Apr 30 | — | May 14 – May 28 | — | 90–110 days | Long-season crop best timed to mature after a light fall frost for sweetest flavor; start indoors 5-7 weeks before last frost. |
| Carrot | — | May 7 – May 21 | — | Jul 6 – Jul 20 | 60–80 days | Direct sow only (does not transplant); sow 2-4 weeks before last frost, as soon as soil can be worked. |
| Beet | — | May 7 – May 21 | — | Jul 20 – Aug 3 | 50–65 days | Direct sow 2-4 weeks before last frost; tolerates light frost. |
| Radish | — | Apr 30 – May 14 | — | Aug 17 – Aug 31 | 22–30 days | Very fast and cold-hardy; direct sow 3-5 weeks before last frost, as soon as soil can be worked. |
| Turnip | — | May 7 – May 21 | — | Jul 20 – Aug 3 | 40–60 days | Cold-hardy; direct sow 2-4 weeks before last frost. |
| Onion | Mar 26 – Apr 9 | — | May 7 – May 21 | — | 90–120 days | Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings. |
| Garlic | — | — | — | Aug 31 – Sep 14 | 240–270 days | Fall-planted crop only; not planted in spring in most climates. |
| Potato | — | May 7 – May 21 | — | — | 70–120 days | Plant seed potatoes 2-4 weeks before last frost, as soon as soil can be worked and is above 45F; light frost on emerging foliage is usually tolerated. |
| Sweet Potato | — | — | Jun 18 – Jul 2 | — | 90–120 days | Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive. |
| Asparagus | — | — | May 7 – May 21 | — | 730–1095 days | Perennial; plant crowns 2-4 weeks before last frost as soon as soil can be worked. Takes 2-3 years to full production. |
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Basil | Apr 23 – Apr 30 | — | Jun 11 – Jun 18 | — | 50–70 days | Very frost/cold sensitive; start indoors 5-6 weeks before last frost, transplant only after all danger of frost (1-2 weeks after) and nights stay warm. |
| Cilantro | — | May 14 – May 28 | — | Aug 3 – Aug 17 | 45–70 days | Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring. |
| Parsley | Apr 9 – Apr 23 | — | May 21 – May 28 | — | 70–90 days | Slow to germinate; start indoors 6-8 weeks before last frost, transplant 1-2 weeks before last frost (biennial, cold-tolerant). |
| Dill | — | May 14 – May 28 | — | — | 40–60 days | Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer. |
| Oregano | Apr 9 – Apr 23 | — | Jun 4 – Jun 11 | — | 80–90 days | Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date. |
| Thyme | Apr 9 – Apr 23 | — | Jun 4 – Jun 11 | — | 85–95 days | Perennial herb, slow from seed; start indoors 6-8 weeks before last frost, transplant around/after last frost. |
| Crop | Start indoors | Direct sow | Transplant | Fall planting | Maturity | Notes |
|---|---|---|---|---|---|---|
| Sunflower | — | Jun 11 – Jun 25 | — | — | 70–100 days | Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting. |
| Zinnia | May 7 – May 14 | Jun 11 – Jun 25 | Jun 11 – Jun 18 | — | 60–70 days | Frost-tender; direct sow 1-3 weeks after last frost, or start indoors 3-4 weeks early for earlier blooms. |
| Marigold | Apr 23 – May 7 | — | Jun 11 – Jun 18 | — | 45–60 days | Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed. |
| Cosmos | May 7 – May 14 | Jun 11 – Jun 25 | Jun 11 – Jun 18 | — | 60–90 days | Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early. |
| Nasturtium | — | Jun 11 – Jun 25 | — | — | 50–65 days | Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed. |
| Dahlia | — | — | Jun 11 – Jun 25 | — | 90–120 days | Plant tubers 1-3 weeks after last frost once soil is warm (60F+); very frost-sensitive. |
Date ranges are estimates based on university extension guidelines and this city's NOAA frost normals — not a guarantee. Scroll to see all columns on narrow screens.
Frequently Asked Questions
When is the last frost in Flagstaff, AZ?
Based on 1991–2020 NOAA climate normals for the FLAGSTAFF PULLIAM AP, AZ US station, the last spring frost in Flagstaff typically falls around June 4. A cautious gardener might wait until June 19 (only a 10% chance of a later frost), while May 21 marks an earlier, higher-risk planting date.
When is the first frost in Flagstaff, AZ in fall?
The first fall frost in Flagstaff typically arrives around September 28. To stay safe, assume frost could start as early as September 16; in milder years it can hold off until October 9.
How long is the growing season in Flagstaff, AZ?
Flagstaff's average frost-free growing season is about 115 days, running from the typical last spring frost (June 4) to the typical first fall frost (September 28).
What USDA hardiness zone is Flagstaff, AZ in?
Flagstaff, AZ is in USDA plant hardiness zone 6a, per the USDA's 2023 Plant Hardiness Zone Map. A classic four-season climate with cold winters and a solid summer growing season.