Watermelon in Portsmouth: weekly temperatures and windows
Detailed weekly chart for this crop and place. For planting dates, see when to plant watermelon in Portsmouth.
Growing window for Watermelon: none (0 days)
Planting window for Watermelon: Jun 8 – Jul 21 (44 days)
Outdoors: weekly temperatures and windows
Temperatures across the year for Portsmouth. 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.
- 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 1 · Jan 1 – Jan 4
Average 4 to 8 °C · Possible −4 to 14 °C
Growing: too cold
Planting: too cold
A week is in range when its average low and high sit inside the tolerance band 16 to 38 °C; it is suitable when that average range also overlaps the ideal 21 to 35 °C band and possible readings stay within 0 °C to 38 °C. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 0 °C) 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 (35 seasons (1991–2025)).
- Ideal
- Tolerable
- Too cold
- Too hot
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.
Dates for Portsmouth use ERA5-Land cell 50.80, -1.09. How we calculated this · Algorithm 2026-10-season-10.