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When to plant tomato in Seattle

How to grow TomatoSeattle climate
Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Tomato in Seattle is a good fit outdoors. The suitable growing window of 127 days covers the 55–90 days this plant usually needs.

Start indoors
March 24 – April 20
Transplant outside
May 23 – June 19
Harvest
July 17 – September 17
Season vs crop
127 grow days vs 55–90 needed
Typical frost (last spring – first fall)
April 2 – October 25

Tomato in Seattle is a good fit outdoors. The suitable growing window of 127 days covers the 55–90 days this plant usually needs.

Planting conditions

Tomato planting activities across the year: Start indoors, Grow indoors, Harden off, Transplant outside, Grow outdoors, HarvestJFMAMJJASOND~Apr 2~Oct 25
  • Start indoors
  • Grow indoors
  • Harden off
  • Transplant outside
  • Grow outdoors
  • Harvest
Local activity windows for this place and growing method. Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost.
Suitable growing days in a row127
Days to harvest55–90 days from transplant
Mar 24 – Apr 20
Start indoors
Apr 21 – May 15
Grow indoors
May 16 – May 22
Harden off
May 23
Transplant outside
May 24 – Jul 16
Grow outdoors
Jul 17 – Sep 17
Harvest
ActivityWindowNotes
Start indoorsMar 24 – Apr 20Sow indoors before the outdoor window.
Grow indoorsApr 21 – May 15Seedlings grow indoors until harden or transplant.
Harden offMay 16 – May 22Acclimate seedlings outdoors before planting.
Transplant outsideMay 23Move plants outside on this day (start of the plant-out window).
Grow outdoorsMay 24 – Jul 16Plants grow outdoors until harvest.
HarvestJul 17 – Sep 17Expected harvest from typical days to harvest.
Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost. Adjust a week or two for your conditions.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (70 – 84 °F) and tolerable (55 – 95 °F) ranges.

Tomato planting and growing weeks in SeattleJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECPlantingGrowing
Planting uses sow / plant-out rules (frost, soil germination, night, and last-sow): green when plantable, blue diagonal when nights or soil are too cold, amber cross-hatch when too hot, faint for other calendar limits. Growing shows daytime air against this plant’s ideal and tolerable ranges across the year.

Key dates

Typical last spring frostApril 2
Safer last spring frostApril 2
Typical first fall frostOctober 25
Safer first fall frostOctober 25
Frost-free days205
Earliest indoor seed startMarch 24
Latest indoor seed startApril 20
Transplant outdoorsMay 23 – June 19
Direct sow windownot recommended here
Suitable growing windowMay 23 – September 26 (127 days)
Expected harvestJuly 17 – September 17

How these dates are judged

Ideal conditions
Daytime air from 70 – 84 °F.
Suitable conditions
Daytime air from 55 – 95 °F.
Last frost and first frost
Typical spring and fall frost dates for Seattle, shown in the key dates.
Days to harvest
55–90 days from transplant, from typical days to harvest.
Sowing window
Dated sow and harvest bars use frost dates, soil minima, night limits, and last-sow count-back from typical crop timing. The year strip and weekly chart use the same window: air ratings only colour weeks inside it.

Growing window for Tomato: May 23 – Sep 26 (127 days)

Planting window for Tomato: May 23 – Jun 19 (28 days)

Usually too cold: Sep 28 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Seattle. Shaded bands are this plant’s ideal and tolerable daytime air ranges. Growing is daytime air suitability; Planting is sow / plant-out conditions (same colour language). Window brackets mark each stretch.

JanFebMarAprMayJunJulAugSepOctNovDec−20 °C−4 °F−10 °C14 °F0 °C32 °F10 °C50 °F20 °C68 °F30 °C86 °F40 °C104 °FTolerable 13–35 °CTolerable 55–95 °FIdeal 21–29 °CIdeal 70–84 °FWindowGrowingMay 23 – Sep 26PlantingMay 23 – Jun 19Last frost ~Apr 2First frost ~Oct 25
  • Ideal range
  • Tolerable range
  • Possible min to max
  • Average min to max
  • Suitable
  • Tolerable
  • Too cold
  • Too hot

Selected week · tap a week or use the arrows

Week 21 · May 18 – May 24

Average 47 to 62 °F · Possible 41 to 79 °F

Growing: too cold

Planting: too cold

A week is in range when its average low and high sit inside the tolerance band 55 to 95 °F; it is suitable when that average range also overlaps the ideal 70 to 84 °F band and possible readings stay within 32 °F to 95 °F. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 32 °F) makes it too cold. When a sowing window is calculated, weeks outside that window are uncoloured even if air is in range.

Based on average frost dates.

Show all 53 weeks
Cover method weekly charts

Outdoor weekly chart is above. Open a cover chart only if you grow under fleece, a cold frame, or an unheated greenhouse.

Other plants for Seattle

Calculated by Plan & Plant · Method · Data 2019–2026

Frost and suitability dates are typical figures from climate statistics. Microclimates vary; they are not a guarantee.

How we calculated this
  • Data: ERA5-Land via Open-Meteo, cell 47.60, -122.30, years 2019–2026 (not a 30-year climate normal yet).
  • Typical and safer dates: Typical last frost is the date after which half of winters in this sample had no more frost; safer is later in the sample so fewer winters still frosted.
  • Crop rule: Local windows for Tomato from frost dates, temperature ratings, and crop timing rules.
  • Confidence: Provisional — short or thin sample for this place.
  • Full methodology (algorithm 2026-10-season-6).

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