September Heat: When Summer Refuses To Leave The UK

There is something slightly strange about being told that it is going to reach 27°C when September is almost over.

By this point in the year, we have usually started thinking about darker evenings, jumpers, heating bills and whether it is too early to put the winter duvet back on the bed. The summer clothes have often been pushed towards the back of the wardrobe, the barbecue has been cleaned for another year and someone has probably already mentioned Christmas.

And yet here we are, with temperatures heading towards 27°C.

It might feel unusually warm for late September, but Britain’s weather has always had the capacity to surprise us. September sits in that awkward position between summer and autumn, and historically it has produced everything from blazing sunshine and temperatures in the thirties to overnight frosts and conditions that feel more like November.

In fact, some of the UK’s most remarkable September heat happened long before most of us were born.

The September that reached 35.6°C

If you think 27°C is impressive for the end of September, imagine 35.6°C.

That is the UK’s highest recorded September temperature, measured at Bawtry in South Yorkshire on 2 September 1906. More than a century later, that record still stands.

The extraordinary heat wasn’t confined to one location. On 1 September that year, Gordon Castle in Moray reached 32.2°C, which remains Scotland’s September record, while Hawarden Bridge in what was then Clwyd reached 32.3°C, the Welsh September record.

So the idea that September can occasionally behave like the middle of summer is nothing new.

What is perhaps surprising is just how long some of these records have survived. The 1906 September heat remains the benchmark for the UK, despite more than a century of changing weather and plenty of memorable hot summers since.

September 2023 gave us a reminder

For a more recent example, look no further than September 2023.

The beginning of that month produced an exceptional spell of heat. According to the Met Office, the UK experienced seven consecutive days with temperatures reaching at least 30°C, the longest such run ever recorded in September. The previous September records had been five consecutive days, in 1929 and 1911.

It was the sort of weather that confused everyone.

Schools had gone back, summer holidays were over and the calendar was telling us that autumn was approaching, but the weather was behaving as though somebody had accidentally left July switched on.

People were still looking for fans, cold drinks and somewhere to sit in the shade while simultaneously trying to remember where they had put their autumn clothes.

And 27°C doesn’t sound quite so strange now

A temperature of 27°C at the end of September can certainly feel unusual, but it isn’t anywhere close to the most extreme conditions Britain has experienced during the month.

The Met Office describes September as a month of extraordinary contrasts. The UK has recorded temperatures above 35°C during September, while the same month has also produced freezing conditions and even a UK September minimum of -6.7°C at Dalwhinnie in Scotland on 26 September 1942.

That is quite a range.

It means that September can effectively give us the final days of summer and the first taste of winter within the same month. In British weather terms, that feels about right.

The end of September can still be summer

There is a tendency to think of the seasons as having clear boundaries.

June is summer. September is autumn. December is winter. March is spring.

The weather, of course, hasn’t read the calendar.

The beginning of September can still feel like August, while the end of the month can occasionally feel distinctly wintry. There is no guarantee that the temperature will gradually decline in a neat and orderly fashion simply because we have turned another page on the calendar.

That is why days like today can feel so enjoyable. When September produces a properly warm day, it feels like a bonus. Summer has technically packed its bags, but it has decided to stay for another cup of tea.

We’ve all experienced the late summer surprise

Most of us probably have our own memories of unexpectedly hot September days.

Perhaps it was going back to school in weather that was still warm enough for shorts. Perhaps you remember sitting outside in the evening and wondering why you had already started putting the garden furniture away. Maybe you went to work wearing something suitable for autumn and spent the afternoon regretting the decision.

There is something particularly British about being caught out by warm weather.

We spend much of the year complaining that it is too cold, too wet or too windy. Then the moment the temperature climbs, we start complaining that it is too hot.

The phrase “It’s too hot for this time of year” is practically part of the national vocabulary.

The heat doesn’t always disappear when the sun goes down

One of the fascinating things about September heat is that it isn’t just daytime temperatures that can be impressive.

The UK’s highest September daily minimum temperature is 21.7°C, recorded at St James’s Park in London on 5 September 1949. In other words, even after the sun had gone down, temperatures remained remarkably high.

For anyone who has ever struggled to sleep during a hot spell, that might be almost as impressive as the daytime record.

A hot September day is one thing. A warm September night is something else entirely.

By late September, we have normally started enjoying the cooler evenings, so a warm night can feel particularly unusual. The windows stay open, the duvet gets pushed aside and somebody inevitably says, “I can’t believe it’s this warm at this time of year.”

September has always been unpredictable

Perhaps the biggest lesson from Britain’s September weather history is that there really is no such thing as a guaranteed September.

The month can bring blazing sunshine, heavy rain, strong winds, frost and even snow-freezing conditions. The Met Office’s historical records show just how wide the range can be.

The UK’s lowest recorded September maximum temperature was just 4.4°C at Braemar in Scotland on 29 September 1915. England’s lowest September maximum was 6.2°C at Malham Tarn in North Yorkshire on 27 September 1974.

So while 27°C today might feel like summer has made an unexpected return, we shouldn’t assume September has suddenly forgotten how to be cold.

It can change its mind very quickly.

The changing meaning of a hot day

There is also something interesting about how we remember hot weather.

Ask someone of a certain age about British heat and you will probably hear stories about 1976. Ask someone else and they might mention 1990, 1995, 2003, 2018 or the extraordinary temperatures of 2022.

Gen X grew up with a very different relationship with hot weather. There was no weather app providing an hourly forecast in your pocket. You looked out of the window, listened to the forecast on the radio or watched the television weather presenter and made your plans accordingly.

A genuinely hot day felt like an event.

Windows were opened. Fans were brought out. Ice lollies became a legitimate food group. People sat outside in the evening because the house was too warm. And somebody inevitably announced that they hadn’t seen weather like it since 1976.

A late September day worth enjoying

There is a temptation to spend a warm day worrying about when the weather is going to change.

But perhaps the best thing about an unexpected September heatwave is simply to enjoy it.

Have lunch outside. Take the dog for a walk. Sit in the garden. Go for a bike ride. Have an ice cream. Open the windows and let some of that late-summer air into the house.

Because we know what is coming.

The evenings will get darker. The mornings will get colder. The heating will go back on. Coats will return to the backs of chairs. The first frost will eventually arrive.

But not quite yet.

Today, September is giving us 27°C, and that is a rather nice reminder that British weather doesn’t always follow the rules we expect it to.

The calendar might be telling us that autumn is here, but the thermometer has other ideas.

And perhaps that is one of the reasons we love talking about the weather so much.

It never quite does what we expect.

Do you remember a September when the weather was so hot that it felt more like the middle of summer? What is the hottest September day you can remember?