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

Planting zone for 85646 — Tubac, AZ

ZIP code 85646 (Tubac, Santa Cruz County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 5 and the first fall frost November 10.

Where ZIP 85646 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.

Zone8b15 to 20 °F
Coldest night−9.4 to −6.7 °C
Last frostApr 5
First frostNov 10
2012 zone8b

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 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Tubac, 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 Tubac, AZ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 5median — 50% chance of a later frost
Safe for tender plantsApril 25only 10% chance of frost after
First fall frostNovember 10median — 10% chance by Oct 21
Growing season217 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 12 and returns around November 20.

From the NOAA station Tumacacori Nm, AZ — 4 miles away, elevation 3,268 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 85646

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 22 – Mar 8
SpinachSow outdoors · Feb 22 – Mar 15
Broccoli, cabbageStart indoors · Jan 25 – Feb 8
Broccoli, cabbageTransplant · Mar 15 – Mar 29
Onion setsPlant outdoors · Mar 8 – Mar 22
PotatoesPlant outdoors · Mar 15 – Mar 29
LettuceSow outdoors · Mar 8 – Mar 22
Carrots, beetsSow outdoors · Mar 15 – Mar 29
TomatoesStart indoors · Feb 8 – Feb 22
TomatoesTransplant · Apr 12 – Apr 26
Peppers, eggplantStart indoors · Jan 25 – Feb 8
Peppers, eggplantTransplant · Apr 19 – May 3
BeansSow outdoors · Apr 12 – Apr 26
Sweet cornSow outdoors · Apr 12 – Apr 26
Cucumbers, squashSow outdoors · Apr 12 – Apr 26
Fall lettuce, spinachSow outdoors · Sep 15 – Sep 29
GarlicPlant cloves · Oct 27 – Dec 1
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 5) and first fall frost (Nov 10) 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 85646 came on Jan 24 — 5 days earlier than the 1991–2020 average (Jan 29).

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).

Soil in Tubac, AZ

The soil mapped at the center of ZIP 85646 is Pinaleno — gravelly sandy loam, well drained.

TextureGravelly sandy loamdrains and warms fast; dries out and needs more feeding
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.25%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Pinalino gravelly sandy loam, 0 to 10 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 85646; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Tubac, AZ

Summer high95 °Faverage high, June
Winter low32 °Faverage low, January
Hot days115days a year at 90 °F or more
Freezing nights60nights a year at 32 °F or less
Growing degree days5,195base 50 °F — the season’s usable heat
Longest day14 h 13 mindaylight on June 21
Shortest day10 h 05 mindaylight on December 21
Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb
Precipitation16.4 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 63 °F, low 32 °F 63°32° JanFebruary: average high 66 °F, low 34 °F 66°34° FebMarch: average high 72 °F, low 38 °F 72°38° MarApril: average high 78 °F, low 43 °F 78°43° AprMay: average high 86 °F, low 49 °F 86°49° MayJune: average high 95 °F, low 59 °F 95°59° JunJuly: average high 93 °F, low 67 °F 93°67° JulAugust: average high 91 °F, low 66 °F 91°66° AugSeptember: average high 89 °F, low 60 °F 89°60° SepOctober: average high 81 °F, low 48 °F 81°48° OctNovember: average high 71 °F, low 38 °F 71°38° NovDecember: average high 63 °F, low 32 °F 63°32° Dec

Precipitation by month inches

0″1″2″3″4″January: 1.09 in precipitation 1.1 JanFebruary: 1.21 in precipitation 1.2 FebMarch: 0.85 in precipitation 0.8 MarApril: 0.36 in precipitation 0.4 AprMay: 0.31 in precipitation 0.3 MayJune: 0.41 in precipitation 0.4 JunJuly: 3.70 in precipitation 3.7 JulAugust: 3.62 in precipitation 3.6 AugSeptember: 1.88 in precipitation 1.9 SepOctober: 0.84 in precipitation 0.8 OctNovember: 0.82 in precipitation 0.8 NovDecember: 1.36 in precipitation 1.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Tumacacori Nm, AZ (4 mi away); precipitation: Tubac 2.9 Sw, AZ (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

856408b
Tumacacori, AZ · 4 mi
856458b
Amado, AZ · 8 mi
856488b
Rio Rico, AZ · 9 mi
856288b
Nogales, AZ · 10 mi
856229a
Green Valley, AZ · 13 mi
856149a
Green Valley, AZ · 15 mi
856018b
Arivaca, AZ · 17 mi
856218b
Nogales, AZ · 18 mi

Arizona planting zones →

Questions about 85646

What planting zone is ZIP code 85646?

ZIP code 85646 (Tubac, AZ) is in USDA hardiness zone 8b on the 2023 map: the coldest night of an average winter reaches 15 to 20 °F (−9.4 to −6.7 °C).

When is the last frost in Tubac, AZ?

The median last spring frost (32 °F) near 85646 is April 5; after April 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Tumacacori Nm station.

When is the first frost in Tubac, AZ?

The median first fall frost near 85646 is November 10, giving a median frost-free growing season of 217 days.

When should I plant tomatoes in 85646?

Start tomato seeds indoors around Feb 8 – Feb 22 and set transplants outside around Apr 12 – Apr 26, one to three weeks after the median last frost.

How much rain and snow does 85646 get?

About 16.4 inches of precipitation a year (NOAA 1991–2020 normals, Tubac 2.9 Sw station).

How hot do summers get in Tubac, AZ?

The average high peaks at 95 °F in June, with about 115 days a year at 90 °F or more.

What kind of soil does 85646 have?

The USDA soil survey maps Pinaleno at the center of ZIP 85646: gravelly sandy loam, well drained, pH about 6.7 (neutral).

Did spring come early in Tubac, AZ in 2026?

Spring leaf-out near 85646 came on Jan 24 in 2026, 5 days earlier than the 1991–2020 average (Jan 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Tubac, AZ?

Short-day onions: the longest day near 85646 is 14 h 13 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.