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

Planting zone for 83349 — Richfield, ID

ZIP code 83349 (Richfield, Lincoln County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 24 and the first fall frost September 26.

Where ZIP 83349 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostMay 24

First frostSep 26

2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Richfield, ID…

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 Richfield, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 24median — 50% chance of a later frost

Safe for tender plantsJune 14only 10% chance of frost after

First fall frostSeptember 26median — 10% chance by Sep 10

Growing season123 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 8 and returns around October 7.

From the NOAA station Richfield, ID — 4 miles away, elevation 4,308 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 83349

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 12 – Apr 26

SpinachSow outdoors · Apr 12 – May 3

Broccoli, cabbageStart indoors · Mar 15 – Mar 29

Broccoli, cabbageTransplant · May 3 – May 17

Onion setsPlant outdoors · Apr 26 – May 10

PotatoesPlant outdoors · May 3 – May 17

LettuceSow outdoors · Apr 26 – May 10

Carrots, beetsSow outdoors · May 3 – May 17

TomatoesStart indoors · Mar 29 – Apr 12

TomatoesTransplant · May 31 – Jun 14

Peppers, eggplantStart indoors · Mar 15 – Mar 29

Peppers, eggplantTransplant · Jun 7 – Jun 21

BeansSow outdoors · May 31 – Jun 14

Sweet cornSow outdoors · May 31 – Jun 14

Cucumbers, squashSow outdoors · May 31 – Jun 14

Fall lettuce, spinachSow outdoors · Aug 1 – Aug 15

GarlicPlant cloves · Sep 12 – Oct 17

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 24) and first fall frost (Sep 26) 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 83349 came on Mar 25 — 21 days earlier than the 1991–2020 average (Apr 15).

average
Apr 152026
Mar 25

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 Richfield, ID

The soil mapped at the center of ZIP 83349 is Kinzie — cobbly silt loam, well drained.

TextureCobbly silt loama good balance for most vegetables

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Kinzie-Marley complex, 6 to 15 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 83349; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Richfield, ID

Summer high89 °Faverage high, July

Winter low14 °Faverage low, January

Hot days37days a year at 90 °F or more

Freezing nights185nights a year at 32 °F or less

Growing degree days2,223base 50 °F — the season’s usable heat

Longest day15 h 23 mindaylight on June 21

Shortest day8 h 59 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation10.5 inper year, rain and melted snow

Snowfall29 inper year; 62 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: Richfield, ID (4 mi away); precipitation: Richfield, ID (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Idaho planting zones →

Questions about 83349

What planting zone is ZIP code 83349?

ZIP code 83349 (Richfield, ID) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Richfield, ID?

The median last spring frost (32 °F) near 83349 is May 24; after June 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Richfield station.

When is the first frost in Richfield, ID?

The median first fall frost near 83349 is September 26, giving a median frost-free growing season of 123 days.

When should I plant tomatoes in 83349?

Start tomato seeds indoors around Mar 29 – Apr 12 and set transplants outside around May 31 – Jun 14, one to three weeks after the median last frost.

How much rain and snow does 83349 get?

About 10.5 inches of precipitation a year and 29 inches of snowfall (NOAA 1991–2020 normals, Richfield station).

How hot do summers get in Richfield, ID?

The average high peaks at 89 °F in July, with about 37 days a year at 90 °F or more.

What kind of soil does 83349 have?

The USDA soil survey maps Kinzie at the center of ZIP 83349: cobbly silt loam, well drained, pH about 7.0 (neutral).

Did spring come early in Richfield, ID in 2026?

Spring leaf-out near 83349 came on Mar 25 in 2026, 21 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Richfield, ID?

Long-day onions: the longest day near 83349 is 15 h 23 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 83349 change?

Yes. The 2012 USDA map put 83349 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.