PlantAlong
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Zone 8a

The coldest winter night here averages 10 to 15°F1. Frost dates vary more than that suggests.

ZIP codes
3,413
Weather stations
650
Last reviewed
Your zone tells you how cold winter gets. It does not tell you when to plant.
Typical last frost
Mar 29most ZIPs Mar 20 – Apr 7
Typical first frost
Nov 6most ZIPs Oct 31 – Nov 14
Spread in spring
18 daysbetween early and late ZIPs
  1. Last spring frostmedian Mar 29
  2. First fall frostmedian Nov 6
  • Frost-free season (median)
Figure 1. When frosts fall across zone 8a: the full range (pale), most ZIP codes (10th to 90th percentile, solid) and the median (marker). From 650 NOAA stations matched to 2,528 ZIP codes.

Zone and frost date are different things. The zone comes from the coldest winter night; frost dates come from spring and fall temperatures at weather stations2. Your own dates can sit anywhere in the range above, so the calendar for your ZIP is the better guide.

Five digits. The calendar is computed on your device.

When to plant in zone 8a

Each crop uses its primary extension source, applied to this zone's frost spread. Rules written for another state are labelled with their source.

  1. Tomatoes
  2. Peppers
  3. Cucumbers
  4. Zucchini
  5. Beans
  6. Peas
  7. Lettuce
  8. Carrots
  9. Onions
  10. Garlic
  11. Potatoes
  12. BasilNo sourced window
  • Start indoors
  • Plant outdoors
  • Range across the zone
  • Frost-free season (median)
  • Spring frost risk (90% to 10%)
  • Fall frost risk (10% to 90%)
Figure 2. Planting windows across zone 8a. Solid and dashed bars: the window at the zone's median frost dates. Pale bars: where the same window falls across most of the zone's ZIP codes.
Table 1. Planting windows in zone 8a.
CropWhatZone medianAcross most of the zoneSource
TomatoesStart indoorsFeb 2Jan 24 – Feb 11Oregon State, central OR3
Transplant outdoorsApr 12Apr 3 – Apr 21Colorado State4
PeppersStart indoorsFeb 16Feb 7 – Feb 25Oregon State, central OR3
Transplant outdoorsApr 12Apr 3 – Apr 21Colorado State4
CucumbersStart indoorsMar 15Mar 6 – Mar 24Oregon State, central OR3
Transplant outdoorsApr 5Mar 27 – Apr 14Oregon State, central OR3
Sow outdoorsMar 29Mar 20 – Apr 7Colorado State4
ZucchiniStart indoorsMar 22Mar 13 – Mar 31Oregon State, central OR3
Transplant outdoorsApr 12Apr 3 – Apr 21Oregon State, central OR3
Sow outdoorsMar 29Mar 20 – Apr 7Colorado State4
BeansStart indoorsMar 8Feb 28 – Mar 17Oregon State, central OR3
Transplant outdoorsApr 5Mar 27 – Apr 14Oregon State, central OR3
Sow outdoorsMar 29Mar 20 – Apr 7Colorado State4
PeasStart indoorsFeb 2Jan 24 – Feb 11Oregon State, central OR3
Transplant outdoorsMar 1Feb 21 – Mar 10Oregon State, central OR3
Sow outdoorsMar 1 – Mar 15Feb 21 – Mar 24Colorado State4
LettuceStart indoorsFeb 9Jan 31 – Feb 18Oregon State, central OR3
Transplant outdoorsMar 15Mar 6 – Mar 24Oregon State, central OR3
Sow outdoorsMar 1 – Mar 15Feb 21 – Mar 24Colorado State4
CarrotsSow outdoorsMar 15 – Mar 29Mar 6 – Apr 7Colorado State4
OnionsStart indoorsDec 8Nov 29 – Dec 17Oregon State, central OR3
Transplant outdoorsFeb 16Feb 7 – Feb 25Oregon State, central OR3
Sow outdoorsMar 1 – Mar 15Feb 21 – Mar 24Colorado State4
GarlicPlant for fallNov 13 – Nov 20Nov 7 – Nov 28Wisconsin5
PotatoesSow outdoorsMar 15 – Mar 29Mar 6 – Apr 7Colorado State4
BasilNo frost-relative rule is published; sources give conditions instead (see the crop page).

Sources

  1. PRISM Group, Oregon State University, 2023 USDA Plant Hardiness Zone Map ZIP code data (PHZM 2023), 2023-11-15. Retrieved 2026-11-02.
  2. NOAA National Centers for Environmental Information, U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), 2021. Retrieved 2026-11-02.
  3. Oregon State University Extension Service, When to start seeds indoors in central Oregon, reviewed 2024. Retrieved 2026-11-02.
  4. Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720), reviewed September 2024. Retrieved 2026-11-02.
  5. University of Wisconsin–Madison Division of Extension, Wisconsin Horticulture, Garlic, Allium sativum, Rev: 10/2023. Retrieved 2026-11-02.