From the Western Isles to Shetland, the islands are maritime through and through: Stornoway's first autumn frost holds off to early November, the latest in Scotland, and hard frost is rare.
The catch is not cold, it is wind and salt. Shelter matters more here than the calendar. There is little high ground in the populated areas, so we give a single maritime figure rather than a lowland/upland split.
Frost dates for Islands
Half-month bands from named Met Office stations (1991-2020 averages). This region is offered as a single maritime figure. See below.
| Garden | Last spring frost | First autumn frost | Safe to plant out | Season | Station | Confidence |
|---|---|---|---|---|---|---|
| lowland | late April | early November | mid May | ~190 days | Stornoway (15m) | high |
Corroborated by Lerwick, Tiree.
Sources: Met Office · Met Office
What this means for growing here
Sow and plant out to these dates rather than a UK calendar, and remember they are regional averages. Your own plot can run two to four weeks later in a frost pocket, or earlier against a warm wall. On exposed island sites, shelter from wind and salt usually does more than chasing an early date.The Planting Calendar turns these into a month-by-month plan.
Sources
- Met Office: location-specific long-term averages: the 1991-2020 air-frost day counts behind every variant row, including the Inverness/Edinburgh comparison
- Derivation method: GrowScotland's own. We treat a month as carrying meaningful frost risk when it averages at least half an air-frost day, take the last such month in spring and the first in autumn, and express each as a half-month band.