Planting zone for 85342 — Morristown, AZ
ZIP code 85342 (Morristown, Maricopa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F.
Where ZIP 85342 is
Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoomNot 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.
Was 9a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9b means →
Frost forecast — next 7 nights
live from the National Weather ServiceLoading the forecast for Morristown, 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
A 32 °F frost doesn't happen here in most winters. At the nearest station (NOAA station Castle Hot Springs, AZ — 6 miles away, elevation 1,992 ft) the median growing season is 341 days. When frost does come, it is a midwinter night or two; cover tender plants when a freeze is forecast.
Frost data: NOAA NCEI U.S. Climate Normals 1991–2020.
When spring arrived in 2026
In 2026, spring leaf-out near 85342 came on Jan 19 — 7 days earlier than the 1991–2020 average (Jan 26).
Jan 262026
Jan 19
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 Morristown, AZ
The soil mapped at the center of ZIP 85342 is Lehmans — gravelly clay loam, well drained.
Map unit: Lehmans extremely rocky clay loam, 8 to 60 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 85342; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Morristown, AZ
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Castle Hot Springs, AZ (6 mi away); precipitation: Castle Hot Springs, AZ (6 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.
Questions about 85342
What planting zone is ZIP code 85342?
ZIP code 85342 (Morristown, AZ) is in USDA hardiness zone 9b on the 2023 map: the coldest night of an average winter reaches 25 to 30 °F (−3.9 to −1.1 °C).
How much rain and snow does 85342 get?
About 14.3 inches of precipitation a year (NOAA 1991–2020 normals, Castle Hot Springs station).
How hot do summers get in Morristown, AZ?
The average high peaks at 105 °F in July, with about 155 days a year at 90 °F or more.
What kind of soil does 85342 have?
The USDA soil survey maps Lehmans at the center of ZIP 85342: gravelly clay loam, well drained, pH about 7.5 (slightly alkaline).
Did spring come early in Morristown, AZ in 2026?
Spring leaf-out near 85342 came on Jan 19 in 2026, 7 days earlier than the 1991–2020 average (Jan 26), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Morristown, AZ?
Intermediate onions: the longest day near 85342 is 14 h 25 min, so day-neutral types bulb best; long-day varieties may not bulb fully.
Did the zone for 85342 change?
Yes. The 2012 USDA map put 85342 in zone 9a; the 2023 map puts it in zone 9b. The newer map uses 1991–2020 data and more weather stations.