When to plant watermelon in San Antonio

In San Antonio, typical last spring frost is January 30 and typical first fall frost is December 24. Typical last spring frost: January 30. Watermelon in San Antonio is a good fit outdoors. The suitable growing window of 219 days covers the 70–100 days this plant usually needs.

Watermelon

How to grow Watermelon San Antonio climate Weekly temperatures and windows

Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Watermelon in San Antonio is a good fit outdoors. The suitable growing window of 219 days covers the 70–100 days this plant usually needs.

When to plantMarch 20 – May 14

Harvest: May 29 – August 22
Season vs crop: 219 grow days vs 70–100 needed
Typical frost (last spring – first fall): January 30 – December 24

Watermelon in San Antonio is a good fit outdoors. The suitable growing window of 219 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. Dashed lines are typical last and first frost.

Suitable growing days in a row219

Days to harvest70–100 days from seed

Mar 20 – May 14

Direct sow

May 15 – May 28

Grow outdoors

May 29 – Aug 22

Harvest

Activity	Window	Notes
Direct sow	Mar 20 – May 14	Plant outdoors in this window.
Grow outdoors	May 15 – May 28	Plants grow outdoors until harvest.
Harvest	May 29 – Aug 22	Expected harvest from typical days to harvest.

Direct sow
Grow outdoors
Harvest

Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost (35 seasons (1991–2025)). 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

Typical last spring frostJanuary 30

Low-risk last spring frostMarch 6

Typical first fall frostDecember 24

Low-risk first fall frostDecember 4

Frost-free days327

Outdoor sow dateMarch 20

Direct sow windowMarch 20 – May 14

Suitable growing windowMarch 20 – October 24 (219 days)

Expected harvestMay 29 – August 22

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 Antonio, 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 Antonio

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 Antonio use ERA5-Land cell 29.42, -98.49. How we calculated this · Algorithm 2026-10-season-10.

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