When to plant watermelon in Phoenix

In Phoenix, typical last spring frost is January 17 and typical first fall frost is December 22. Typical last spring frost: January 17. Watermelon in Phoenix is doable with planning outdoors. 78 suitable days are enough for fast varieties (70 days) but not slow ones (100 days).

Watermelon

How to grow Watermelon Phoenix climate Weekly temperatures and windows

Where are you growing?

Tight fit

Not realistic in greenhouse

Comfortable in a cold frame

Watermelon in Phoenix is doable with planning outdoors. 78 suitable days are enough for fast varieties (70 days) but not slow ones (100 days).

When to plantMarch 22 – May 16

Harvest: May 31 – August 24
Season vs crop: 78 grow days vs 70–100 needed
Typical frost (last spring – first fall): January 17 – December 22

Watermelon in Phoenix is doable with planning outdoors. 78 suitable days are enough for fast varieties (70 days) but not slow ones (100 days).

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 row78

Days to harvest70–100 days from seed

Mar 22 – May 16

Direct sow

May 17 – May 30

Grow outdoors

May 31 – Aug 24

Harvest

Activity	Window	Notes
Direct sow	Mar 22 – May 16	Plant outdoors in this window.
Grow outdoors	May 17 – May 30	Plants grow outdoors until harvest.
Harvest	May 31 – Aug 24	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 17

Low-risk last spring frostFebruary 22

Typical first fall frostDecember 22

Low-risk first fall frostNovember 30

Frost-free days338

Outdoor sow dateMarch 22

Direct sow windowMarch 22 – May 16

Suitable growing windowMarch 22 – June 7 (78 days)

Expected harvestMay 31 – August 24

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 Phoenix, 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 Phoenix

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 Phoenix use ERA5-Land cell 33.45, -112.07. How we calculated this · Algorithm 2026-10-season-10.

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