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When to plant tomato in Ottawa

How to grow TomatoOttawa climate
Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Tomato in Ottawa is a good fit outdoors. The suitable growing window of 100 days covers the 55–90 days this plant usually needs.

Start indoors
March 28 – April 25
Transplant outside
May 27 – June 24
Harvest
July 21 – September 3
Season vs crop
100 grow days vs 55–90 needed
Typical frost (last spring – first fall)
May 13 – October 30

Tomato in Ottawa is a good fit outdoors. The suitable growing window of 100 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~May 13~Oct 30
  • 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 row100
Days to harvest55–90 days from transplant
Mar 28 – Apr 25
Start indoors
Apr 26 – May 19
Grow indoors
May 20 – May 26
Harden off
May 27
Transplant outside
May 28 – Jul 20
Grow outdoors
Jul 21 – Sep 3
Harvest
ActivityWindowNotes
Start indoorsMar 28 – Apr 25Sow indoors before the outdoor window.
Grow indoorsApr 26 – May 19Seedlings grow indoors until harden or transplant.
Harden offMay 20 – May 26Acclimate seedlings outdoors before planting.
Transplant outsideMay 27Move plants outside on this day (start of the plant-out window).
Grow outdoorsMay 28 – Jul 20Plants grow outdoors until harvest.
HarvestJul 21 – Sep 3Expected 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 (21 – 29 °C) and tolerable (13 – 35 °C) ranges.

Tomato planting and growing weeks in OttawaJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECPlantingGrowing
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 frostMay 13
Safer last spring frostMay 13
Typical first fall frostOctober 30
Safer first fall frostOctober 30
Frost-free days169
Earliest indoor seed startMarch 28
Latest indoor seed startApril 25
Transplant outdoorsMay 27 – June 24
Direct sow windownot recommended here
Suitable growing windowMay 27 – September 3 (100 days)
Expected harvestJuly 21 – September 3

How these dates are judged

Ideal conditions
Daytime air from 21 – 29 °C.
Suitable conditions
Daytime air from 13 – 35 °C.
Last frost and first frost
Typical spring and fall frost dates for Ottawa, 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 27 – Sep 3 (100 days)

Planting window for Tomato: May 27 – Jun 24 (29 days)

Usually too cold: Jan 1 – May 24; Sep 14 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Ottawa. 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−40 °C−40 °F−30 °C−22 °F−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 27 – Sep 3PlantingMay 27 – Jun 24Last frost ~May 13First frost ~Oct 30
  • 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 22 · May 25 – May 31

Average 11 to 23 °C · Possible 4 to 33 °C

Growing: too cold (inside window)

Planting: suitable

A week is in range when its average low and high sit inside the tolerance band 13 to 35 °C; it is suitable when that average range also overlaps the ideal 21 to 29 °C band and possible readings stay within 0 °C to 35 °C. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 0 °C) 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 Ottawa

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 45.41, -75.70, 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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