Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for Flagstaff, AZ

Flagstaff, AZ is in USDA zones 6a to 7a across its 5 ZIP codes. The median last spring frost is June 4 and the first fall frost September 28.

Flagstaff on the zone map

Outlined: its 4 ZIP code areas · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zones6a–7a−10 to 5 °F
ZIP codes5
Last frostJun 4
First frostSep 28
Growing season115 days

6a 3 ZIPs   6b 1 ZIP   7a 1 ZIP

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Flagstaff, AZ…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Flagstaff, AZ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 4median — 50% chance of a later frost
Safe for tender plantsJune 19only 10% chance of frost after
First fall frostSeptember 28median — 10% chance by Sep 16
Growing season115 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 20 and returns around October 9.

From the NOAA station Flagstaff Pulliam Airport, AZ, elevation 7,005 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in Flagstaff

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 23 – May 7
SpinachSow outdoors · Apr 23 – May 14
Broccoli, cabbageStart indoors · Mar 26 – Apr 9
Broccoli, cabbageTransplant · May 14 – May 28
Onion setsPlant outdoors · May 7 – May 21
PotatoesPlant outdoors · May 14 – May 28
LettuceSow outdoors · May 7 – May 21
Carrots, beetsSow outdoors · May 14 – May 28
TomatoesStart indoors · Apr 9 – Apr 23
TomatoesTransplant · Jun 11 – Jun 25
Peppers, eggplantStart indoors · Mar 26 – Apr 9
Peppers, eggplantTransplant · Jun 18 – Jul 2
BeansSow outdoors · Jun 11 – Jun 25
Sweet cornSow outdoors · Jun 11 – Jun 25
Cucumbers, squashSow outdoors · Jun 11 – Jun 25
Fall lettuce, spinachSow outdoors · Aug 3 – Aug 17
GarlicPlant cloves · Sep 14 – Oct 19
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 4) and first fall frost (Sep 28) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 86002 came on Mar 10 — 31 days earlier than the 1991–2020 average (Apr 10).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 6a in Arizona

436 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 22

Arizona cypress50 ft · blooms spring · low shade tolerance · to −23 °FArizona walnut50 ft · blooms late spring · high shade tolerance · to −33 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblue spruce100 ft · blooms late spring · medium shade tolerance · to −38 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °Fbristlecone pine40 ft · blooms mid summer · high shade tolerance · to −33 °F

Shrubs 87

alderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican tarwort3 ft · blooms late spring · high shade tolerance · to −23 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FApache plume6 ft · blooms late spring · high shade tolerance · to −23 °Fbig sagebrush4 ft · blooms mid summer · high shade tolerance · to −43 °F

Wildflowers & perennials 185

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 135

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °FArizona cottontop4 ft · blooms late summer · high shade tolerance · to −13 °FArizona fescue2 ft · blooms late spring · high shade tolerance · to −23 °F

Vines 1

western white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Flagstaff, AZ.

Soil in Flagstaff, AZ

The soil mapped at the center of ZIP 86002 is Lynx — loam, well drained.

TextureLoama good balance for most vegetables
pH8.0alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Lynx loam, 0 to 2 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 86002; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Flagstaff, AZ

Summer high82 °Faverage high, July
Winter low17 °Faverage low, December
Hot days3days a year at 90 °F or more
Freezing nights202nights a year at 32 °F or less
Growing degree days1,723base 50 °F — the season’s usable heat
Longest day14 h 32 mindaylight on June 21
Shortest day9 h 47 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation22.1 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 43 °F, low 18 °F 43°18° JanFebruary: average high 46 °F, low 20 °F 46°20° FebMarch: average high 52 °F, low 24 °F 52°24° MarApril: average high 59 °F, low 28 °F 59°28° AprMay: average high 68 °F, low 35 °F 68°35° MayJune: average high 79 °F, low 43 °F 79°43° JunJuly: average high 82 °F, low 51 °F 82°51° JulAugust: average high 79 °F, low 51 °F 79°51° AugSeptember: average high 74 °F, low 43 °F 74°43° SepOctober: average high 64 °F, low 32 °F 64°32° OctNovember: average high 52 °F, low 23 °F 52°23° NovDecember: average high 43 °F, low 17 °F 43°17° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.30 in precipitation 2.3 JanFebruary: 2.35 in precipitation 2.4 FebMarch: 2.02 in precipitation 2.0 MarApril: 1.12 in precipitation 1.1 AprMay: 0.80 in precipitation 0.8 MayJune: 0.44 in precipitation 0.4 JunJuly: 2.73 in precipitation 2.7 JulAugust: 3.68 in precipitation 3.7 AugSeptember: 1.74 in precipitation 1.7 SepOctober: 1.54 in precipitation 1.5 OctNovember: 1.41 in precipitation 1.4 NovDecember: 1.98 in precipitation 2.0 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Flagstaff Pulliam Airport, AZ (4 mi away); precipitation: Flagstaff 2.2 Sw, AZ (2 mi away). Daylight is calculated from latitude.

ZIP codes in Flagstaff

860016a
−10 to −5 °F
860026a
−10 to −5 °F
860037a
0 to 5 °F
860046b
−5 to 0 °F
860056a
−10 to −5 °F

Arizona planting zones →

Questions about Flagstaff

What planting zone is Flagstaff, AZ?

Flagstaff, AZ is in USDA hardiness zones 6a to 7a on the 2023 map (6a: −10 to −5 °F; 6b: −5 to 0 °F; 7a: 0 to 5 °F).

When is the last frost in Flagstaff, AZ?

The median last spring frost is June 4 and the median first fall frost is September 28 (NOAA 1991–2020 normals, Flagstaff Pulliam Airport station).

When can I plant a garden in Flagstaff, AZ?

Cool-season crops like peas and spinach go in around Apr 23 – May 14; tomatoes, peppers, beans and squash after about Jun 11, once frost risk has passed.

What kind of onions grow in Flagstaff, AZ?

Intermediate onions: the longest day is 14 h 32 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

How much rain and snow does Flagstaff, AZ get?

About 22.1 inches of precipitation a year (NOAA 1991–2020 normals).