When to plant chili pepper in Portsmouth

In Portsmouth, typical last spring frost is March 23 and typical first fall frost is December 1. Typical last spring frost: March 23. Chili pepper in Portsmouth is not realistic outdoors: 0 suitable days are fewer than the 60 days this plant usually needs.

Chili pepper

How to grow Chili pepper Portsmouth climate Weekly temperatures and windows

Where are you growing?

Not realistic outdoors

Not realistic in greenhouse

Comfortable in a cold frame

Chili pepper in Portsmouth is a good fit under fleece. The suitable growing window of 100 days covers the 60–100 days this plant usually needs.

Start indoors: March 6 – April 30
Transplant outside: May 8 – July 2
Harvest: July 7 – October 10
Season vs crop: 100 grow days vs 60–100 needed
Typical frost (last spring – first fall): February 14 – December 29

Chili pepper in Portsmouth is a good fit under fleece. The suitable growing window of 100 days covers the 60–100 days this plant usually needs.

Estimate. Protection varies with the cover, the weather and how you vent it.

Fleece adds about 1–4 °C on frosty nights, depending on its weight. Remove it on warm days.

Fleece also cuts light: about 5–10 % for light fleece, up to 50–70 % for heavy grades. Take it off by day once frosts are over.

Cover dates are modelled from weather-model data using published greenhouse studies. They are not measured in your greenhouse. A max–min thermometer inside will tell you more.

Typical last frost estimate range February 21 – January 17, depending on the cover and the night.

Planting conditions

Start indoors
Harden off
Transplant outside
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 row100

Days to harvest60–100 days from transplant

Mar 6 – Apr 30

Start indoors

May 1 – May 7

Harden off

May 8

Transplant outside

May 9 – Jul 6

Grow outdoors

Jul 7 – Oct 10

Harvest

Activity	Window	Notes
Start indoors	Mar 6 – Apr 30	Sow indoors before the outdoor window.
Harden off	May 1 – May 7	Acclimate seedlings outdoors before planting.
Transplant outside	May 8	Move plants outside on this day (start of the plant-out window).
Grow outdoors	May 9 – Jul 6	Plants grow outdoors until harvest.
Harvest	Jul 7 – Oct 10	Expected harvest from typical days to harvest.

Start indoors
Harden off
Transplant outside
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.

Protected frost and sowing dates are modelled estimates from weather-model data and published greenhouse studies, not measured in your greenhouse. A max–min thermometer inside will tell you more.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (21 – 32 °C70 – 90 °F21 – 32 °C (70 – 90 °F)) and tolerable (16 – 35 °C61 – 95 °F16 – 35 °C (61 – 95 °F)) ranges, from modelled cover temperatures for the growing method you selected.

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 14

Low-risk last spring frostMarch 5

Typical first fall frostDecember 29

Low-risk first fall frostNovember 30

Frost-free days317

Earliest indoor seed startMarch 6

Latest indoor seed startApril 30

Transplant outdoorsMay 8 – July 2

Direct sow windownot recommended here

Suitable growing windowMay 8 – August 15 (100 days)

Expected harvestJuly 7 – October 10

How these dates are judged

Ideal conditions: Daytime air from 21 – 32 °C70 – 90 °F21 – 32 °C (70 – 90 °F).
Suitable conditions: Daytime air from 16 – 35 °C61 – 95 °F16 – 35 °C (61 – 95 °F).
Last frost and first frost: Typical spring and fall frost dates for Portsmouth, shown in the key dates.
Days to harvest: 60–100 days from transplant, 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 Portsmouth

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 Portsmouth use ERA5-Land cell 50.80, -1.09. How we calculated this · Algorithm 2026-10-season-10.

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