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When to plant sweet corn in San Francisco

How to grow Sweet cornSan Francisco climate
Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Sweet corn in San Francisco is a good fit outdoors. The suitable growing window of 278 days covers the 60–90 days this plant usually needs.

When to plantJanuary 15 – December 4

Harvest
March 16 – October 19
Season vs crop
278 grow days vs 60–90 needed

Sweet corn in San Francisco is a good fit outdoors. The suitable growing window of 278 days covers the 60–90 days this plant usually needs.

Planting conditions

Sweet corn planting activities across the year: Direct sow, HarvestJFMAMJJASOND
  • Direct sow
  • Harvest
Local activity windows for this place and growing method. Blue fill is usually too cold for this plant.
Suitable growing days in a row278
Days to harvest60–90 days from seed
Jan 15 – Dec 4
Direct sow
Mar 16 – Oct 19
Harvest
ActivityWindowNotes
Direct sowJan 15 – Dec 4Plant outdoors in this window.
HarvestMar 16 – Oct 19Expected harvest from typical days to harvest.
Blue fill is usually too cold for this plant. 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 – 90 °F) and tolerable (55 – 95 °F) ranges.

Sweet corn planting and growing weeks in San FranciscoJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECPlantingGrowing
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

Frost-free daysNot yet (short archive)
Outdoor sow dateJanuary 15
Direct sow windowJanuary 15 – December 4
Suitable growing windowJanuary 15 – October 19 (278 days)
Expected harvestMarch 16 – October 19

How these dates are judged

Ideal conditions
Daytime air from 70 – 90 °F.
Suitable conditions
Daytime air from 55 – 95 °F.
Last frost and first frost
Typical spring and fall frost dates for San Francisco, shown in the key dates.
Days to harvest
60–90 days from seed, 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 Sweet corn: Jan 15 – Oct 19 (278 days)

Planting window for Sweet corn: Jan 15 – Dec 4 (324 days)

Usually too cold: Jan 1 – Jan 11

Outdoors: weekly temperatures and windows

Temperatures across the year for San Francisco. 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−10 °C14 °F0 °C32 °F10 °C50 °F20 °C68 °F30 °C86 °F40 °C104 °FTolerable 13–35 °CTolerable 55–95 °FIdeal 21–32 °CIdeal 70–90 °FWindowGrowingJan 15 – Oct 19PlantingJan 15 – Dec 4No typical frost here. Timing follows heat, not frost.
  • 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 3 · Jan 12 – Jan 18

Average 44 to 58 °F · Possible 37 to 73 °F

Growing: too cold (inside window)

Planting: suitable

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 90 °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 San Francisco

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 37.77, -122.42, 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 Sweet corn 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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