USDA Hardiness Zone 6a
Frost Dates for 86001 — Flagstaff, Arizona
Averages from Ft Valley, Az US, the nearest reporting station, 1.4 miles away.
Plant tender crops after June 11, and expect the first autumn freeze around September 25. That leaves about 99 frost-free days.
- Last spring frost
- June 11
- First fall frost
- September 25
- Growing season
- 99 days
- Hardiness zone
- 6a
50% probability
50% probability
frost-free
-10 to -5°F annual low
Planting calendar for 86001
| When | What to do |
|---|---|
| April 2 – April 16 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| April 16 – April 30 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| May 14 – May 28 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| June 11 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by July 3 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by September 11 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 25 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after June 11 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Flagstaff, Arizona are past their last freeze. Harvest before September 25, which leaves roughly 99 frost-free days.
ZIP 86001 sits in USDA hardiness zone 6a, meaning the average coldest night of the year falls between -10 to -5°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.