Last and first frost dates in Portsmouth

When is the last frost in Portsmouth?

The last frost in Portsmouth usually comes around 4 March: that is the median of 2016–2025, so in about half of those years the last night at or below 0 °C came later. Hardy crops start before it and frost-tender ones only after it: in the table below arugula can go into open ground from 11 February, while corn waits until 19 April. The first autumn frost follows around 1 December, about 272 days later: harvest or cover frost-tender crops before then.

When to sow and plant

Planting out: a week after the last frost once the soil is warm enough for the crop; frost-hardy crops three weeks before it; an unheated greenhouse three weeks earlier. Seedlings are sown so they are ready on that day. Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.

When the soil warms up in Portsmouth

The day the top 7 cm of soil first averages each temperature over a week, median of 2016–2025 (ERA5 via Open-Meteo). The soil reaches 10 °C 32 days after the last spring frost and 15 °C 78 days after it.

Frost dates near Portsmouth

Of the nearest cities on our list, the last spring frost ends earliest in Brighton (8 February) and latest in Bristol (11 April).

Seeds, seedlings and markets in Portsmouth

Within 15 km of Portsmouth OpenStreetMap lists 16 garden centres, 4 plant nurseries, 5 markets and 8 farm shops (collected 28 October 2026). The nearest garden centre to the city centre is Alver Valley, 6 km away.

• Alver Valley — garden centre
  Barrington Close, PO13 8NZ Gosport · Mon–Sat 09:00–17:30; Sun 10:30–16:30 · 6 km · yourlocalgardencentre.co.uk
• Rumsey Gardens — plant nursery
  Drift Road 117, PO8 0PD Clanfield · 15 km · rumsey-gardens.co.uk
• Waterlooville Pop up Shop — market
  Wellington Way 31, Waterlooville · Mon–Sat 09:00–17:00 · 9 km
• Stoke Fruit Farm — farm shop
  Havant Road 77, PO11 0PT Hayling Island · Mon–Sat 08:30–17:30; Sun 09:30–16:00 · 8 km · stokefruitfarm.co.uk
• Meadow Farm Nursery and Tea Room — garden centre
  Woodgaston Lane, Hayling Island · 9 km
• Bumbles — market
  High Street 40, PO33 4PL Ryde · 14 km

• Where to buy seeds and seedlings in Portsmouth
• Selling your own harvest in the United Kingdom

Places: © OpenStreetMap contributors, ODbL.

Weather in Portsmouth by month

Average weather in Portsmouth over 2016–2025: the warmest month is July. Months that average 20 °C or more by day: July (20.7 °C) and August (20.7 °C). No month averages below 0 °C at night; the coldest nights, in January, average 3.4 °C. About 883 mm of rain falls in a year, on 145 days; October is the wettest month (108 mm) and April the driest (45 mm).

Average of the daily highs and lows, rain per month and days with at least 1 mm (ERA5 via Open-Meteo, the same grid cell as the frost dates).

Planted in autumn

From a month before the first autumn frost, so the roots grow before winter, to the late-planting limit on each crop’s page (about two weeks before the ground freezes, by ten years of weather).