Frost dates Washington Spokane

Frost dates in Spokane, Washington

Last spring frost Apr 26 First fall frost Oct 15 NOAA 1991-2020

The average last spring frost in Spokane is Apr 26 and the average first fall frost is Oct 15, measured at SPOKANE FELTS FLD, about 5 miles from the city centre. Below: how sure those dates are, and what to start, sow and set out each week.

Average last spring frostApr 2632°F, 50% probability
Average first fall frostOct 1532°F, 50% probability
Days between them172average frost-free season
How sure is that date? NOAA probability levels for a 32°F freeze
ProbabilityFreeze still comes after (spring)First freeze has come by (fall)
90%Apr 10Oct 31
50%Apr 26Oct 15
10%May 10Sep 30

Read it like this: in half of years the last 32°F freeze of spring comes after Apr 26, and in 1 year in 10 there is still a freeze after May 10. In 1 year in 10 the first fall freeze arrives before Sep 30.

Measured at: SPOKANE FELTS FLD, WA (NOAA station USW00094176), about 5 miles away at 1,953 ft, 22 years of record in 1991-2020.

Other stations nearby, for comparison:

  • SPOKANE INTL AP, WA (NOAA station USW00024157), about 5 miles away at 2,353 ft, 26 years of record in 1991-2020: last spring frost Apr 26, first fall frost Oct 12
  • SPOKANE WFO, WA (NOAA station USC00457941), about 9 miles away at 2,392 ft, 22 years of record in 1991-2020: last spring frost May 10, first fall frost Sep 26

Seed-starting schedule for Spokane, WA

Counted from a last frost date of Apr 26 (the average: a freeze comes later than this in half of years).

  1. Week of Jan 1814 weeks before last frost
    • Start seeds indoorsLeekJan 18 to Feb 1
    • Start seeds indoorsOnionJan 18 to Feb 1
  2. Week of Jan 2513 weeks before last frost
    • Start seeds indoorsParsleyJan 25 to Feb 1
  3. Week of Feb 112 weeks before last frost
    • Start seeds indoorsCeleryFeb 1 to Feb 15
    • Start seeds indoorsSpinachFeb 1 to Feb 15
  4. Week of Feb 1510 weeks before last frost
    • Start seeds indoorsBroccoliFeb 15 to Mar 1
    • Start seeds indoorsBrussels sproutFeb 15 to Mar 1
    • Start seeds indoorsCabbageFeb 15 to Mar 1
    • Start seeds indoorsKaleFeb 15 to Mar 1
    • Start seeds indoorsKohlrabiFeb 15 to Mar 1
  5. Week of Feb 229 weeks before last frost
    • Start seeds indoorsLettuceFeb 22 to Mar 1
  6. Week of Mar 18 weeks before last frost
    • Start seeds indoorsCauliflowerMar 1 to Mar 15
    • Start seeds indoorsEggplantMar 1 to Mar 15
    • Start seeds indoorsPepperMar 1 to Mar 15
    • Start seeds indoorsSwiss chardMar 1 to Mar 15
  7. Week of Mar 87 weeks before last frost
    • Start seeds indoorsTomatoMar 8 to Mar 22
  8. Week of Mar 156 weeks before last frost
    • Start seeds indoorsBasilMar 15 to Mar 29
    • Set transplants outSpinachMar 15 to Apr 5
  9. Week of Mar 294 weeks before last frost
    • Sow seed outdoorsRadishMar 29 to Apr 12
    • Sow seed outdoorsSwiss chardfrom Mar 29
    • Sow seed outdoorsTurnipMar 29 to Apr 12
    • Set transplants outBroccoliMar 29 to Apr 12
    • Set transplants outBrussels sproutMar 29 to Apr 12
    • Set transplants outCabbagefrom Mar 29
    • Set transplants outKalefrom Mar 29
    • Set transplants outKohlrabifrom Mar 29
    • Set transplants outLeekfrom Mar 29
    • Set transplants outLettuceMar 29 to Apr 5
    • Set transplants outOnionfrom Mar 29
  10. Week of Apr 53 weeks before last frost
    • Start seeds indoorsCucumberApr 5 to Apr 12
    • Set transplants outParsleyApr 5 to Apr 12
  11. Week of Apr 122 weeks before last frost
    • Start seeds indoorsMelonApr 12 to Apr 19
    • Start seeds indoorsPumpkinApr 12 to Apr 19
    • Start seeds indoorsSummer squashApr 12 to Apr 19
    • Start seeds indoorsWinter squashApr 12 to Apr 19
    • Start seeds indoorsZucchiniApr 12 to Apr 19
    • Plant seed potatoes outdoorsPotatoApr 12 to Apr 19
    • Set transplants outCauliflowerfrom Apr 12
    • Set transplants outSwiss chardfrom Apr 12
  12. Week of Apr 26Last frost week
    • Sow seed outdoorsBeanfrom Apr 26
    • Sow seed outdoorsParsnipfrom Apr 26
    • Set transplants outCeleryfrom Apr 26
  13. Week of May 31 week after last frost
    • Plant slips outdoorsSweet potatoMay 3 to May 10
    • Set transplants outCucumberMay 3 to May 10
    • Set transplants outTomatoMay 3 to May 10
  14. Week of May 102 weeks after last frost
    • Set transplants outBasilfrom May 10
    • Set transplants outEggplantMay 10 to May 17
    • Set transplants outMelonfrom May 10
    • Set transplants outPepperfrom May 10
    • Set transplants outPumpkinfrom May 10
    • Set transplants outSummer squashfrom May 10
    • Set transplants outWinter squashfrom May 10
    • Set transplants outZucchinifrom May 10

Not in the city centre? Look up your own ZIP code

More in Washington

Where the numbers come from

Sources and method

Frost dates. U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), NOAA National Centers for Environmental Information (Palecki, Durre, Applequist, Arguez and Lawrimore, 2021). These are 30-year station statistics for 1991 to 2020. "Frost" here means an air temperature of 32°F or lower at the station. We use 6,539 stations that have at least 10 years of record and a published date; 176 more are stations where a freeze is too rare for NOAA to date, and 180 are stations cold enough to have frost risk all year.

Probability level. The headline dates are NOAA's 50% level: in half of years the last spring freeze comes later than that date, and in half of years the first fall freeze comes earlier. The 10% and 90% levels are shown next to them. For tender plants, the 10% spring date is the safer one to plan from: a freeze follows it in only 1 year in 10.

Which station. Your ZIP code is matched to the nearest of those stations by straight-line distance from the ZIP code's centre point (GeoNames, geonames.org, CC BY 4.0; 40,979 ZIP codes in the 50 states and DC). Nearest is not always most alike: a station on a hill, in a valley or by the water can differ from your garden by a week or more. That is why the station's name, distance and elevation are shown with every result, along with two more stations nearby. NOAA makes the same point: the normals are limited between stations as distance grows horizontally and vertically.

Seed-starting offsets. Growing Vegetables: When to Plant Your Vegetable Garden, a fact sheet from University of New Hampshire Extension. It gives each crop's weeks from seed to transplant and when it is safe to set out or sow relative to the last frost. The method is theirs too: take the planting date and count back the seed-to-transplant weeks. Where the fact sheet gives a range of planting dates, the start-indoors dates count back from the earliest one. The figures used, as the fact sheet states them:

  • Basil: Seed to transplant 6-8 weeks; set out 2 weeks after last frost.
  • Bean: Plant seed in garden after last frost.
  • Broccoli: Seed to transplant 4-6 weeks; set out 2-4 weeks before last frost.
  • Brussels sprout: Seed to transplant 4-6 weeks; set out 2-4 weeks before last frost.
  • Cabbage: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Cauliflower: Seed to transplant 4-6 weeks; set out 2 weeks before last frost.
  • Celery: Seed to transplant 10-12 weeks; set out after last frost.
  • Cucumber: Seed to transplant 3-4 weeks; set out 1-2 weeks after last frost.
  • Eggplant: Seed to transplant 8-10 weeks; set out 2-3 weeks after last frost.
  • Kale: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Kohlrabi: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Leek: Seed to transplant 8-10 weeks; set out 4 weeks before last frost.
  • Lettuce: Seed to transplant 4-5 weeks; set out 3-4 weeks before last frost.
  • Melon: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Onion: Seed to transplant 8-10 weeks; set out 4 weeks before last frost.
  • Parsley: Seed to transplant 9-10 weeks; set out 2-3 weeks before last frost.
  • Parsnip: Plant seed in garden after last frost.
  • Pepper: Seed to transplant 8-10 weeks; set out 2 weeks after last frost.
  • Potato: Plant seed potatoes in garden 1-2 weeks before last frost.
  • Pumpkin: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Radish: Plant seed in garden 2-4 weeks before last frost.
  • Spinach: Seed to transplant 4-6 weeks; set out 3-6 weeks before last frost.
  • Summer squash: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Sweet potato: Plant slips in garden 1-2 weeks after last frost.
  • Swiss chard: Seed to transplant 4-6 weeks; set out 2 weeks before last frost; or plant seed in garden 4 weeks before last frost.
  • Tomato: Seed to transplant 6-8 weeks; set out 1-2 weeks after last frost.
  • Turnip: Plant seed in garden 2-4 weeks before last frost.
  • Winter squash: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Zucchini: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.

Not on the calendar. The same fact sheet times these by soil temperature, not by frost date, so they get no date here:

  • Pea: as soon as the soil thaws.
  • Beet: when the soil warms to 45°F.
  • Carrot: when the soil warms to 60°F.
  • Corn: when the soil warms to 60°F.
  • Cucumber, pumpkin, summer squash, winter squash, zucchini: direct-sow when the soil warms to 70°F.

Rutabaga is left out: the fact sheet gives it New Hampshire calendar dates, not a frost offset.

The fact sheet was written for New Hampshire. The offsets are relative to the last frost, so they carry to other places with a spring frost, but where winters are mild many cool-season crops are grown in fall and winter instead. Your state's extension service has the local calendar. Dates are 30-year statistics, not a forecast: check the forecast before setting tender plants out.

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