Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 86003 — Flagstaff, AZ

ZIP code 86003 (Flagstaff, Coconino County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 14 and the first fall frost October 25.

Where ZIP 86003 is

Outlined: the ZIP code area · 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.

Zone7a0 to 5 °F

Coldest night−17.8 to −15 °C

Last frostApr 14

First frostOct 25

2012 zone7a

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7a means →

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 frostApril 14median — 50% chance of a later frost

Safe for tender plantsMay 4only 10% chance of frost after

First fall frostOctober 25median — 10% chance by Oct 11

Growing season192 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 30 and returns around November 7.

From the NOAA station Twin Arrows, AZ — 6 miles away, elevation 5,814 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 86003

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 3 – Mar 17

SpinachSow outdoors · Mar 3 – Mar 24

Broccoli, cabbageStart indoors · Feb 3 – Feb 17

Broccoli, cabbageTransplant · Mar 24 – Apr 7

Onion setsPlant outdoors · Mar 17 – Mar 31

PotatoesPlant outdoors · Mar 24 – Apr 7

LettuceSow outdoors · Mar 17 – Mar 31

Carrots, beetsSow outdoors · Mar 24 – Apr 7

TomatoesStart indoors · Feb 17 – Mar 3

TomatoesTransplant · Apr 21 – May 5

Peppers, eggplantStart indoors · Feb 3 – Feb 17

Peppers, eggplantTransplant · Apr 28 – May 12

BeansSow outdoors · Apr 21 – May 5

Sweet cornSow outdoors · Apr 21 – May 5

Cucumbers, squashSow outdoors · Apr 21 – May 5

Fall lettuce, spinachSow outdoors · Aug 30 – Sep 13

GarlicPlant cloves · Oct 11 – Nov 15

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 14) and first fall frost (Oct 25) 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 86003 came on Feb 23 — 14 days earlier than the 1991–2020 average (Mar 9).

average
Mar 92026
Feb 23

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 7a in Arizona

457 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. Each links to its USDA PLANTS profile.

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 86003 is Mellenthin — gravelly sandy loam, well drained.

TextureGravelly sandy loamdrains and warms fast; dries out and needs more feeding

pH8.1alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.8%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Mellenthin gravelly sandy loam, 0 to 8 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 86003; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Flagstaff, AZ

Summer high90 °Faverage high, July

Winter low24 °Faverage low, January

Hot days49days a year at 90 °F or more

Freezing nights103nights a year at 32 °F or less

Growing degree days3,452base 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

Precipitation12.3 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Twin Arrows, AZ (6 mi away); precipitation: Meteor Crater, AZ (17 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

4 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

860046b

Flagstaff, AZ · 14 mi

860357a

Leupp, AZ · 15 mi

860026a

Flagstaff, AZ · 26 mi

860056a

Flagstaff, AZ · 26 mi

860386b

Mormon Lake, AZ · 28 mi

860477a

Winslow, AZ · 33 mi

860177a

Munds Park, AZ · 34 mi

860247a

Happy Jack, AZ · 40 mi

All 5 ZIP codes in Flagstaff → · Arizona planting zones →

Questions about 86003

What planting zone is ZIP code 86003?

ZIP code 86003 (Flagstaff, AZ) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Flagstaff, AZ?

The median last spring frost (32 °F) near 86003 is April 14; after May 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Twin Arrows station.

When is the first frost in Flagstaff, AZ?

The median first fall frost near 86003 is October 25, giving a median frost-free growing season of 192 days.

When should I plant tomatoes in 86003?

Start tomato seeds indoors around Feb 17 – Mar 3 and set transplants outside around Apr 21 – May 5, one to three weeks after the median last frost.

How much rain and snow does 86003 get?

About 12.3 inches of precipitation a year (NOAA 1991–2020 normals, Meteor Crater station).

How hot do summers get in Flagstaff, AZ?

The average high peaks at 90 °F in July, with about 49 days a year at 90 °F or more.

What kind of soil does 86003 have?

The USDA soil survey maps Mellenthin at the center of ZIP 86003: gravelly sandy loam, well drained, pH about 8.1 (alkaline).

Did spring come early in Flagstaff, AZ in 2026?

Spring leaf-out near 86003 came on Feb 23 in 2026, 14 days earlier than the 1991–2020 average (Mar 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Flagstaff, AZ?

Intermediate onions: the longest day near 86003 is 14 h 32 min, so day-neutral types bulb best; long-day varieties may not bulb fully.