Updated: 2026-08-28
If you live in Glasgow and want to plan around the arrival of summer, the most reliable reference is the Met Office station at Paisley (Renfrewshire), located at 32 metres above sea level and about 11.4 km from the city centre. Across the full period with complete records — 1914 through 2026 — the earliest summer start on record at Paisley is June 1, and it has happened in five separate years: 1918, 1922, 1934, 1978 and 2009. That is the single most concrete answer to "when does summer start": the first day of June, no earlier, in more than a century of observations.
But the story is not just about extremes. The table below shows the summer by year series — the date on which summer conditions first arrive each year at the Paisley measuring point, according to the Met Office MIDAS archive. What stands out is how variable a Scottish summer can be. In 1919, summer held off until July 25. In 1938, it waited until August 11. Yet in 1934, it arrived on June 1, tied with 1918 for the earliest in the entire record. That 92-day gap between the earliest and latest starts defines the range of uncertainty any Glaswegian faces when interpreting "summer" in the forecast.
It's worth clarifying that Paisley is the closest official measuring point to Glasgow, not a reading taken inside the city. Local conditions — urban heat, the Clyde valley, higher ground to the north — can shift actual dates by a few days in either direction. But for a long-term, consistent picture of how summer has been changing over more than a century, this station is the best and most honest reference we have.
Look at the extremes table and you'll see something striking. The five latest summer starts are 1961 (August 30), 1965 (August 13), 1938 (August 11), 2004 (August 8) and 2002 (August 2). The five earliest are all June 1: 1918, 1922, 1934, 1978 and 2009. So within the same 112-year record, summer has started on the first of June in years separated by 91 years — and has been delayed to late August in years as recent as 2004. The variability is not a recent phenomenon: 1938 and 1961 both posted August starts, while the 1970s and 2000s produced several June 1 arrivals.
This is the complete series of summer onset dates at Paisley. Each date marks the first day of the season as defined by the Met Office's seasonal criteria — the moment the station's readings cross the threshold into summer conditions. Note that some years are absent between 1925 and 1929, and again in the 1980s, when the daily record at this station has gaps.
The chart shows the complete annual series. The table lists the most notable years; the full series comes from Met Office.
| Year | Summer Start Date |
|---|---|
| 1914 | 1914-06-16 |
| 2003 | 2003-06-27 |
| 2004 | 2004-08-08 |
| 2005 | 2005-07-12 |
| 2006 | 2006-06-11 |
| 2008 | 2008-07-25 |
| 2009 | 2009-06-01 |
To understand what drives early or late summers, it helps to look at the overall temperature of each year. The five warmest years on record at Paisley are 2006 (10.52°C mean), 2007 (10.45°C), 2004 (10.37°C), 2005 (10.33°C) and 1949 (10.26°C) — four of the five have occurred since 2004. The coldest five are 1993 (7.66°C), 1919 (8.17°C), 1979 (8.21°C), 1965 (8.39°C) and 1963 (8.40°C). Note that 1919 was both the third-coldest year and the year of a late summer start on July 25, while 1965 combined the fourth-coldest year with an August 13 start. By contrast, the warmest year of the series, 2006, saw summer arrive on June 11 — a full two months before the 1961 extreme.
Summer's start is only half the story. The Met Office data also tracks winter frost days — mornings when the temperature at Paisley drops to or below freezing. Across the 97 complete winter seasons in this series, the average number of frost days is 27.82. That is a key figure for gardeners, farmers and anyone tracking the spring transition: on average, roughly a month of winter mornings below 0°C stands between autumn and the March warm-up that precedes summer's onset. A shorter winter frost season typically means an earlier start to thermal spring, which in turn nudges summer's arrival earlier in the year.
If you live in Glasgow, the honest answer to "when does summer start" is: between June 1 and August 30, with the median sitting somewhere in late June or early July. The Paisley station, your nearest official reference, records a June start in most years — but the August outliers of 1938, 1961, 1965, 2002 and 2004 are a reminder that "summer" in western Scotland is a negotiated term. Plan for the June median, prepare for the July possibility, and remember that the same station has posted a June 1 start five times in 112 years — the earliest it ever gets. The climate here gives you early summers in some decades and late ones in others, and that variability is exactly what the official record shows.
Source: Met Office MIDAS (Integrated Data Archive System), Paisley station, Renfrewshire. Period: 1914–2026.
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