Last and first frost dates in Sion

When is the last frost in Sion?

The last frost in Sion usually comes around 8 May: 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 17 April, while corn waits until 27 May. The first autumn frost follows around 19 October, about 164 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 Sion

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 6 days after the last spring frost and 15 °C 44 days after it.

Frost dates near Sion

Of the nearest cities on our list, the last spring frost ends earliest in Lausanne (12 April) and latest in Aosta (6 June).

Seeds, seedlings and markets in Sion

Within 15 km of Sion OpenStreetMap lists 4 garden centres, 1 farm-supply shop, 1 plant nursery, 1 market and 4 farm shops (collected 27 October 2026). The nearest garden centre to the city centre is Point Vert, 5 km away.

• Point Vert — garden centre
  Mon–Thu 08:00–18:30; Sat 08:00–17:00; Fri 08:00–20:00 · 5 km
• Marché de la vieille ville — market
  Fri 08:00–14:00 · 0 km · mvvsion.ch
• Ferme Vuissoz — farm shop
  Chemin de Maragnène 40, 1950 · 2 km · ferme-vuissoz.ch
• Multiplants — garden centre
  Route des Charmilles 42, 1963 Vétroz · 6 km · multiplants.ch
• bioverger.ch — farm shop
  24/7 · 4 km · bioverger.ch
• Agrol — garden centre
  Route de Sion 90, 3960 Sierre · Mon–Thu 08:00–18:30; Fri 08:00–20:00; Sat 08:00–17:00 · 13 km · agrol.ch

• Where to buy seeds and seedlings in Sion
• Selling your own harvest in Switzerland

Places: © OpenStreetMap contributors, ODbL.

Weather in Sion by month

Average weather in Sion over 2016–2025: the warmest month is August. Months that average 20 °C or more by day: June (20.2 °C), July (21.8 °C) and August (22 °C). Nights average below 0 °C in November–April (-7.3–-0.1 °C). About 1413 mm of rain falls in a year, on 170 days; May is the wettest month (160 mm) and February the driest (88 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).