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

Planting zone for 84756 — Newcastle, UT

ZIP code 84756 (Newcastle, Iron County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 31 and the first fall frost September 20.

Where ZIP 84756 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.

Zone5b−15 to −10 °F

Coldest night−26.1 to −23.3 °C

Last frostMay 31

First frostSep 20

2012 zone6a

Was 6a on the 2012 map — half a zone colder now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Newcastle, UT…

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 Newcastle, UT

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 31median — 50% chance of a later frost

Safe for tender plantsJune 20only 10% chance of frost after

First fall frostSeptember 20median — 10% chance by Sep 6

Growing season110 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 17 and returns around September 29.

From the NOAA station Enterprise Beryl Jct, UT — 6 miles away, elevation 5,151 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 84756

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 19 – May 3

SpinachSow outdoors · Apr 19 – May 10

Broccoli, cabbageStart indoors · Mar 22 – Apr 5

Broccoli, cabbageTransplant · May 10 – May 24

Onion setsPlant outdoors · May 3 – May 17

PotatoesPlant outdoors · May 10 – May 24

LettuceSow outdoors · May 3 – May 17

Carrots, beetsSow outdoors · May 10 – May 24

TomatoesStart indoors · Apr 5 – Apr 19

TomatoesTransplant · Jun 7 – Jun 21

Peppers, eggplantStart indoors · Mar 22 – Apr 5

Peppers, eggplantTransplant · Jun 14 – Jun 28

BeansSow outdoors · Jun 7 – Jun 21

Sweet cornSow outdoors · Jun 7 – Jun 21

Cucumbers, squashSow outdoors · Jun 7 – Jun 21

Fall lettuce, spinachSow outdoors · Jul 26 – Aug 9

GarlicPlant cloves · Sep 6 – Oct 11

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 31) and first fall frost (Sep 20) 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 84756 came on Mar 11 — 15 days earlier than the 1991–2020 average (Mar 26).

average
Mar 262026
Mar 11

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 5b in Utah

517 plants native to the lower 48 states, recorded in Utah, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. 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 Newcastle, UT.

Soil in Newcastle, UT

The soil mapped at the center of ZIP 84756 is Antelope Springs — loam, well drained.

TextureLoama good balance for most vegetables

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Antelope Springs 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 84756; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Newcastle, UT

Summer high93 °Faverage high, July

Winter low12 °Faverage low, December

Hot days52days a year at 90 °F or more

Freezing nights203nights a year at 32 °F or less

Growing degree days2,375base 50 °F — the season’s usable heat

Longest day14 h 47 mindaylight on June 21

Shortest day9 h 33 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation15.2 inper year, rain and melted snow

Snowfall25 inper year; 26 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Enterprise Beryl Jct, UT (6 mi away); precipitation: Enterprise, UT (15 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

847145b

Beryl, UT · 14 mi

847206b

Cedar City, UT · 17 mi

847226b

Central, UT · 18 mi

847257a

Enterprise, UT · 19 mi

847537a

Modena, UT · 23 mi

847816b

Pine Valley, UT · 24 mi

847577a

New Harmony, UT · 25 mi

847827b

Veyo, UT · 26 mi

Utah planting zones →

Questions about 84756

What planting zone is ZIP code 84756?

ZIP code 84756 (Newcastle, UT) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Newcastle, UT?

The median last spring frost (32 °F) near 84756 is May 31; after June 20 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Enterprise Beryl Jct station.

When is the first frost in Newcastle, UT?

The median first fall frost near 84756 is September 20, giving a median frost-free growing season of 110 days.

When should I plant tomatoes in 84756?

Start tomato seeds indoors around Apr 5 – Apr 19 and set transplants outside around Jun 7 – Jun 21, one to three weeks after the median last frost.

How much rain and snow does 84756 get?

About 15.2 inches of precipitation a year and 25 inches of snowfall (NOAA 1991–2020 normals, Enterprise station).

How hot do summers get in Newcastle, UT?

The average high peaks at 93 °F in July, with about 52 days a year at 90 °F or more.

What kind of soil does 84756 have?

The USDA soil survey maps Antelope Springs at the center of ZIP 84756: loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Newcastle, UT in 2026?

Spring leaf-out near 84756 came on Mar 11 in 2026, 15 days earlier than the 1991–2020 average (Mar 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Newcastle, UT?

Intermediate onions: the longest day near 84756 is 14 h 47 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 84756 change?

Yes. The 2012 USDA map put 84756 in zone 6a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.