USDA hardiness zone
Zone 1a
Rolled up from the 5 ZIP codes in our data that are classified zone 1a, covering 0 nurseries and garden centers across 0 cities we track in this zone.
Average minimum winter temperature
-60°F
Frost
Frost is rare or absent across most of this zone; timing here follows temperature, not a spring/fall frost date. Any single ZIP's own exact frost status is on that ZIP's own lookup page, not approximated here.
Average frost-free growing season
94 days
Average monthly temperature
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| -13.1° | -5.6° | 2.4° | 25.7° | 46° | 59° | 60.4° | 53.5° | 41.4° | 20.9° | -1.3° | -7.6° |
NOAA 1991–2020 Climate Normals, averaged across this zone's member ZIPs.
Crops by frost hardiness
What grows here, and when
Frost is rare or absent here, so cool-season (hardy/semi-hardy) crops typically go in during the cooler months and warm-season (tender/very-tender) crops before the hottest months arrive, rather than on a frost-relative schedule.
Planting windows and crop timing here are computed from USDA/NOAA climate data and the university extension sources cited below, not a site visit or soil test. Treat this as a starting point: local conditions vary, and a local nursery or extension office can advise on your exact site. See our full Disclaimer.
Hardy (49)
- Apple (bare-root fruit tree)
- Apricot (bare-root fruit tree)
- Asparagus
- Bachelor's Button (Cornflower)
- Bare-root rose
- Blackberry
- Blueberry
- Broccoli
- Brussels Sprouts
- Cabbage
- Calendula
- Catnip/Catmint
- Cherry (sweet/tart, bare-root fruit tree)
- Chives
- Collards
- Currant
- Deciduous shade tree (generic, e.g. maple/oak, bare-root or B&B)
- Elderberry
- Evergreen shrub (B&B/potted, e.g. arborvitae, boxwood)
- Flowering deciduous shrub (generic, e.g. lilac/forsythia)
- Garden Peas
- Garlic
- Gooseberry
- Kale
- Kohlrabi
- Larkspur
- Lavender
- Lettuce
- Mint
- Onion (bulb)
- Oregano
- Peach (bare-root fruit tree)
- Pear (bare-root fruit tree)
- Plum (bare-root fruit tree)
- Radish
- Raspberry
- Rhubarb
- Rutabaga
- Sage
- Snapdragon
- Snow Peas
- Spinach
- Strawberry
- Sweet Alyssum
- Sweet Pea
- Table/Bunch Grape
- Tarragon
- Thyme
- Turnip
Semi-hardy (16)
Tender (20)
Zone 1a means an average annual extreme minimum winter temperature of -60°F to -55°F, the coldest five-degree band the 2023 USDA Plant Hardiness Zone Map draws anywhere in the country. USDA/ARS built that map with the PRISM Climate Group at Oregon State University from 1991-2020 temperature records. USDA publishes no official ZIP-code lookup for it; every ZIP behind this rollup carries its zone matched by centroid against the map, not by the map's own polygon boundary, through phzmapi.org's ZIP-level derivation.
This page reads "frost is rare or absent" above, and for zone 1a that line is wrong for the reason you'd think. Only 2 of this zone's 5 ZIPs have a NOAA weather station close enough to report a real last- and first-frost date; the other 3 simply have no matched station on file. Where a match exists, the last frost lands around May 22 to 25 and the first fall frost around August 24 to 26 (NOAA 1991-2020 Climate Normals), the shortest frost-free stretch this directory measures anywhere. That is a data gap, not a mild winter.
We hold zero nurseries with a ZIP in zone 1a. Every ZIP here sits in Alaska's interior and north.
Nearby zones
All zones
USDA 2023 Plant Hardiness Zone Map (zone boundaries, via the phzmapi.org ZIP-level derivation) and NOAA 1991–2020 Climate Normals (frost dates, growing season, monthly temperatures).