When to plant watermelon in Riverside

In Riverside, typical last spring frost is February 5 and typical first fall frost is December 19. Typical last spring frost: February 5. Watermelon in Riverside is a good fit outdoors. The suitable growing window of 161 days covers the 70–100 days this plant usually needs.

Watermelon

How to grow Watermelon Riverside climate Weekly temperatures and windows

Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Watermelon in Riverside is a good fit outdoors. The suitable growing window of 161 days covers the 70–100 days this plant usually needs.

When to plantApril 19 – June 13

Harvest: June 28 – September 21
Season vs crop: 161 grow days vs 70–100 needed
Typical frost (last spring – first fall): February 5 – December 19

Watermelon in Riverside is a good fit outdoors. The suitable growing window of 161 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 row161

Days to harvest70–100 days from seed

Apr 19 – Jun 13

Direct sow

Jun 14 – Jun 27

Grow outdoors

Jun 28 – Sep 21

Harvest

Activity	Window	Notes
Direct sow	Apr 19 – Jun 13	Plant outdoors in this window.
Grow outdoors	Jun 14 – Jun 27	Plants grow outdoors until harvest.
Harvest	Jun 28 – Sep 21	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 frostFebruary 5

Low-risk last spring frostFebruary 28

Typical first fall frostDecember 19

Low-risk first fall frostNovember 30

Frost-free days316

Outdoor sow dateApril 19

Direct sow windowApril 19 – June 13

Suitable growing windowApril 19 – September 26 (161 days)

Expected harvestJune 28 – September 21

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 Riverside, 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 Riverside

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 Riverside use ERA5-Land cell 33.95, -117.40. How we calculated this · Algorithm 2026-10-season-10.

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