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USDA hardiness zone

Zone 9a

Rolled up from the 2,197 ZIP codes in our data that are classified zone 9a, covering 2,634 nurseries and garden centers across 391 cities we track in this zone.

Average minimum winter temperature

20°F

Last spring frost range

Jan 24–Jun 10

First fall frost range

Sep 13–Dec 28

Average frost-free growing season

266 days

Average monthly temperature

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
49.3° 52.6° 58.1° 64° 71.2° 77.2° 80.2° 80.1° 75.7° 66.7° 57° 50.6°

NOAA 1991–2020 Climate Normals, averaged across this zone's member ZIPs.

Crops by frost hardiness

What grows here, and when

This zone's own last-frost dates range across Jan 24–Jun 10. Hardy and semi-hardy crops can go in before that date; tender and very-tender crops need to wait until after it. See each crop's own guide for exact windows at a specific location in this zone.

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.

Find your exact zone by ZIP →

Zone 9a means an average annual extreme minimum winter temperature of 20°F to 25°F on the 2023 USDA Plant Hardiness Zone Map (USDA/ARS with the PRISM Climate Group at Oregon State University, 1991-2020 records). Every ZIP here carries its zone matched by centroid against the map, not by its polygon boundary, through phzmapi.org's ZIP-level derivation.

The last-frost range above reaches back into January at some of this zone's own ZIPs, real readings, not a rounding artifact, that put nearly a full year of growing within reach at this zone's mildest edge.

We track nurseries across 13 states in zone 9a, from Alabama and Louisiana to Washington and Wisconsin, with Mobile, AL carrying the most, followed by Seattle, WA and San Antonio, TX. Seattle sharing this zone with Mobile is winter-cold math at work, not a shared summer climate; the two cities have almost nothing else in common weather-wise.

Cities we track in zone 9a

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).