Updated: 2026-07-31
The point of measurement closest to Glasgow is the station at Aberfoyle (Perthshire-in-Central-Region), situated at 28 m above sea level, about 35.6 km from the city centre. These are its historical records — the best local reference for frost risk, though Glasgow's own climate may differ due to urban heat, the River Clyde, or local valley effects. The data below covers the period from 1968 to 2001.
Below you will find the full monthly context, but the single most important date to keep in mind is 14 September 2001, when the last frost of the entire record was registered. The following sections explain how the risk evolves month by month, so you can plan around the cold season with confidence.
If you are planning to plant tender seedlings or schedule an outdoor event, the key date to remember is 14 September 2001, when the thermometer at Aberfoyle dipped to -0.5 °C — the most recent frost on record.
This was the latest sub-zero minimum temperature registered in the entire seriesThat is not an isolated oddity. September frosts are rare but they do happen here, and the monthly averages below show just how close to freezing the nights get for much of the year. For a gardener or a farmer, the practical question is not if frost will come, but when — and the answer, based on this station's 34-year record, is that you should not assume the cold season is over until well into spring, nor that it starts only in late autumn.
The table below shows the mean minimum temperature for each month at Aberfoyle. Values below 0 °C indicate months where frost is a regular feature. February stands out as the coldest month, with a mean minimum of -0.9 °C — the only month in the year with a sub-zero monthly average. January and March hover right at the freezing mark (0.1 °C each), meaning frosts are common but not constant. The warmest nights occur in August, with a mean minimum of 9.3 °C, followed closely by July at 9.0 °C. The months from June to September — the traditional growing season — all average above 7.0 °C, but the September figure of 7.0 °C reminds us that the season ends early here.
| Month | Mean Minimum (°C) |
|---|---|
| January | 0.1 |
| February | -0.9 |
| March | 0.1 |
| April | 1.6 |
| May | 4.5 |
| June | 7.0 |
| July | 9.0 |
| August | 9.3 |
| September | 7.0 |
| October | 5.0 |
| November | 1.4 |
| December | 0.7 |
Look at the progression: February's mean minimum of -0.9 °C is the deep freeze, but the real surprise is how late frost can linger. April's mean minimum of 1.6 °C may sound safe, but that is just an average — individual nights can still drop below zero. The recorded frost on 14 September 2001, with a minimum of -0.5 °C, is the clearest warning: even early autumn is not entirely safe. By October, with a mean minimum of 5.0 °C, the risk grows again, and November's 1.4 °C brings frost back into the realm of near-certainty on clear nights.
For comparison, the warmest summer months — July and August, with mean minima of 9.0 °C and 9.3 °C respectively — offer the only true frost-free window. June and September, both at 7.0 °C, are generally safe but not invulnerable, as the 2001 September frost demonstrates.
The complete series at Aberfoyle runs from 1 January 1968 to 1 October 2001. During that entire period, the very last frost registered was the one on 14 September 2001. This does not mean frosts occur every year in September — it means that when the station stopped recording on 1 October 2001, the most recent sub-zero reading was from mid-September of that same year. In other words, the 2001 season was one where frost arrived unusually early, and it serves as a worst-case reference for anyone planning around the autumn equinox.
The practical takeaway for Glasgow-area growers: the safe window for frost-sensitive plants is narrow. If you wait until June (mean minimum 7.0 °C) you are almost certainly safe, but you sacrifice early growth. If you plant in April (mean minimum 1.6 °C), you are gambling against nights that can still dip below freezing. The September 2001 reading of -0.5 °C is your benchmark for the earliest autumn frost on record — plan your harvest accordingly.
Source: Met Office — Aberfoyle station, 1968–2001 period. Data from the Met Office MIDAS archive, official national weather records.
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