When to plant watermelon in San Diego

Local planting windows for Watermelon in San Diego. Frost-free days: 365. Watermelon in San Diego is a good fit outdoors. The suitable growing window of 218 days covers the 70–100 days this plant usually needs.

Watermelon

How to grow Watermelon San Diego climate Weekly temperatures and windows

Where are you growing?

Tight fit

Tight fit in greenhouse

Tight fit in a cold frame

Watermelon in San Diego is a good fit outdoors. The suitable growing window of 218 days covers the 70–100 days this plant usually needs.

When to plantOctober 1 – November 25

Harvest: December 10 – March 5
Season vs crop: 218 grow days vs 70–100 needed

Watermelon in San Diego is a good fit outdoors. The suitable growing window of 218 days covers the 70–100 days this plant usually needs.

Planting conditions

Direct sow
Grow outdoors
Harvest

Local activity windows for this place and growing method. Blue fill is usually too cold for this plant.

Suitable growing days in a row218

Days to harvest70–100 days from seed

Oct 1 – Nov 25

Direct sow

Nov 26 – Dec 9

Grow outdoors

Dec 10 – Mar 5

Harvest

Activity	Window	Notes
Direct sow	Oct 1 – Nov 25	Plant outdoors in this window.
Grow outdoors	Nov 26 – Dec 9	Plants grow outdoors until harvest.
Harvest	Dec 10 – Mar 5	Expected harvest from typical days to harvest.

Direct sow
Grow outdoors
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 (21 – 35 °C70 – 95 °F21 – 35 °C (70 – 95 °F)) and tolerable (16 – 38 °C61 – 100 °F16 – 38 °C (61 – 100 °F)) ranges.

Ideal / plantable
Tolerable
Too cold
Too hot
Outside window

Planting uses sow / plant-out rules; growing shows daytime air against this plant’s ideal and tolerable ranges.

Key dates

Frost-free days365

Outdoor sow dateOctober 1

Direct sow windowOctober 1 – November 25

Suitable growing windowMarch 7 – October 10 (218 days)

Expected harvestDecember 10 – March 5

How these dates are judged

Ideal conditions: Daytime air from 21 – 35 °C70 – 95 °F21 – 35 °C (70 – 95 °F).
Suitable conditions: Daytime air from 16 – 38 °C61 – 100 °F16 – 38 °C (61 – 100 °F).
Last frost and first frost: Typical spring and fall frost dates for San Diego, shown in the key dates.
Days to harvest: 70–100 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. Air ratings on the weekly chart colour only weeks inside that same window — see weekly temperatures and windows.

Other plants for San Diego

Calculated by Plan & Plant. Method. Data 35 seasons (1991–2025).

Frost and suitability dates are typical figures from climate statistics.

Based on 35 years (1991–2025) of ERA5-Land data from Open-Meteo, for an area of about 10 km. Typical dates, not a guarantee.

Dates for San Diego use ERA5-Land cell 32.72, -117.16. How we calculated this · Algorithm 2026-10-season-10.

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