{"id":7013,"date":"2026-09-08T12:11:16","date_gmt":"2026-09-08T11:11:16","guid":{"rendered":"https:\/\/marriott-stats.com\/nigels-blog\/?p=7013"},"modified":"2026-09-08T12:11:16","modified_gmt":"2026-09-08T11:11:16","slug":"uk-weather-trends-summer-2026","status":"publish","type":"post","link":"https:\/\/marriott-stats.com\/nigels-blog\/uk-weather-trends-summer-2026\/","title":{"rendered":"UK Weather Trends #42 – Summer 2026"},"content":{"rendered":"

The 2026 meteorological summer in the UK was the warmest on record, surpassing the record set last year<\/a>.\u00a0 Unlike 2025 whose record was due to steady warmth, 2026 came from a series of heatwaves.\u00a0 Despite that none of the 3 months individually set new records but as a collective, they added up to a new temperature record.<\/p>\n

It was also the 6th sunniest summer on record but whilst it was drier than usual, the dryness was not unusual.\u00a0 That might surprise those experiencing hosepipe bans in certain places but this was due to significant regional variations in rainfall.\u00a0 Consequently, whilst 2026 can be regarded as the 3rd “best summer” of all time through the lens of the 1st principal component, it still had some way to go reach the folklore of 1976 and 1995.\u00a0 More than that, since we have now had two “nice” summers in a row, history tells us these have never been followed by a 3rd “nice” summer so plan accordingly for 2027!<\/p>\n

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Meteorologists define summer in the UK to be the period from June to August so summer is now over and we are officially in autumn.<\/p>\n

I analyse the long term trends in the UK weather using a statistical tool known as Standardisation<\/strong><\/a>.\u00a0 This means the three key variables of Temperature, Sunshine and Rainfall are recalculated so that they all have the same units, which is number of standard deviations above or below the mean.\u00a0 Such variables are known as Z-Scores<\/strong>\u00a0which by definition will have a mean value of 0<\/strong> and a standard deviation of 1<\/strong>.\u00a0 For more information on how I have done this, please read my post on trends in the UK summer of 2017.<\/a><\/p>\n

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Latest Z-Scores<\/strong><\/span><\/h5>\n

The Z-Scores for Temperature, Sunshine and Rainfall are shown in the three charts below.\u00a0 Each chart also contains an 11-year<\/strong> centred moving average which gives an idea of the underlying trend.<\/p>\n

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** In Spring 2024, I added the Z-Score plot below for Rain Intensity<\/strong> since the Met Office has released more historical data.\u00a0 Rain Intensity is the average rainfall per rainy day as opposed to rainfall per day shown in the Rainfall chart.\u00a0 I use this variable as a proxy for how stormy or calm the weather has been.\u00a0 For now, I do not include rain intensity in my analysis of long term trends.\u00a0<\/em><\/span><\/p>\n

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Standardised variables aid interpretation of data in many ways.\u00a0 If the standardised value is positive, it means that the value is above your average or expected value.\u00a0 If it is negative, then the value is below your expected value. \u00a0If the original variable is approximately normal in its distribution then the vertical scale gives us an idea of how typical or atypical each year is.<\/p>\n

Z-Scores in the range -1<\/strong> to +1<\/strong> are considered typical values and completely unremarkable.\u00a0 Z-scores in the ranges -2<\/strong> to -1<\/strong> and +1<\/strong> to +2<\/strong> are considered to be uncommon values but still entirely plausible and such values should not cause us concern.\u00a0 When Z-Scores get into the ranges -3<\/strong> to -2<\/strong> and +2<\/strong> to +3<\/strong>, we should start paying closer attention and asking ourselves if something has changed especially if we get a sequence of successive points in these ranges. Finally, if the Z-scores are less than -3<\/strong> or greater than +3,<\/strong> that is normally regarded as a clear call to action.<\/p>\n

There are in fact many ways of interpreting Z-Scores and\u00a0what I have said so far\u00a0merely a gives an overview of the most basic interpretations.\u00a0 A whole field of study known as Statistical Process Control (SPC) <\/a>is dedicated to building and interpreting such charts (known as Control Charts).<\/p>\n

For the summer of 2026, the z-scores for temperature, sunshine and rainfall were respectively +2.5<\/strong>, +1.8<\/strong> and -0.7<\/strong>.\u00a0 This is the second time temperatures have been more than two standard deviations above the mean of the last 50 years, the first occasion being last year.<\/p>\n

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Long Term Climate Trends<\/strong><\/span><\/h5>\n

Since the moving averages in the above charts all use the same units, they can be plotted onto the same chart as below.\u00a0 For now I do not include rain intensity in this chart.<\/p>\n

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This clearly shows a shift in our summer climate over the last 100<\/strong> years of more than 2<\/strong> standard deviations for temperature.\u00a0 Recall the baseline for the z-score calculation is based on the idea of “living memory<\/em>” which I have defined to be the last 50 years of 1976 to 2025. \u00a0 We can characterise our summers broadly as follows:<\/p>\n