You can plant cucumbers outside once the soil and air are reliably warm and all danger of frost has passed, typically about 1–2 weeks after your local last spring frost date, when nights stay above about 12–15°C (50–60°F).

Quick scoop: the timing

  • Cucumbers are a warm‑season crop with zero frost tolerance, so putting them out too early can stunt or kill them.
  • Aim for:
    • Soil temps in at least the low 20s °C (around 70°F).
* Daytime above ~21°C (70°F) and nights above 12–15°C (50–60°F).
  • For many temperate climates this ends up being:
    • About 1–2 weeks after your average last frost date.
* Often late May to early June for direct sowing or planting seedlings outdoors in cooler regions.

Rule of thumb: if you’re still getting chilly nights or flirting with frost, it’s too early for cucumbers outside.

By method: seeds vs. seedlings

Direct sowing seeds outside

  • Sow once the last frost has passed and the soil has warmed in early summer.
  • Many guides suggest late May or early June in cooler areas, earlier in warmer regions, as long as soil is warm and nights are mild.

Planting started seedlings outside

  • Start seeds indoors a couple of weeks before your last frost date, then transplant 1–2 weeks after that date when it’s reliably warm.
  • Harden off plants first, then plant out once night temps consistently stay above 12°C (53°F) or so.

Climate tweaks and microclimates

  • In cooler climates: treat cucumbers as a true summer crop and wait for warm, settled weather; using cloches or mini greenhouses can help early plantings.
  • In warmer climates: they can often go out earlier in spring and sometimes again for a fall crop, as long as you avoid frost and extreme heat above ~32°C (90°F).
  • A sheltered, south‑facing wall or patio can create a warmer microclimate that lets you plant slightly earlier.

Simple example

If your average last frost is around April 30:

  1. Start seeds indoors around mid– to late April.
  1. Watch the forecast; once nights are staying above 10–12°C (50–53°F) and no frost is predicted, start hardening off.
  1. Plant outside roughly mid‑May or a bit later if nights are still cool.

Mini TL;DR

  • Wait until:
    • No frost in the forecast.
* Soil is warm (around 21–30°C / 70–85°F).

* Nights are consistently mild (above ~12–15°C / 50–60°F).
  • In many regions, that means planting cucumbers outside from late May into early June, but your exact date depends on your local last frost and temperatures.

Information gathered from public forums or data available on the internet and portrayed here.