Is Spring becoming warmer and drier in the UK?

Introduction

Is Spring becoming warmer and drier in the UK? Just a year ago, as the first Lockdown began, the UK was basking in the sunniest and warmest April on record, which was also very dry until the final three days. This was followed by one of the driest, sunniest and warmest Mays on record.

And only six weeks ago in late March, much of the UK was basking in summer-like temperatures. On the 30th, Kew Gardens reached 24.5ºC which was the warmest March day since 1968, whilst the temperature at our Tempestº weather station reached 22.5ºC here in Dorset.

At the beginning of April there was a dramatic change in our weather as a plunge of unusually cold Arctic air engulfed the country on the 4th, bringing widespread snowfall to the north, showers of graupel elsewhere and frequent night frosts. This regime has persisted into May.

Many people are asking whether Climate Change is altering our spring weather. We were interested to determine, using our own data, whether Springs, and particularly Aprils, are becoming colder, warmer or drier. The results are interesting…

Note: The data below was recorded by our Davis Vantage Vue personal weather station. We have only been running our WeatherFlow Tempestº since January 2021 but the data are remarkably similar. For example the Tempestº recorded a mean April temperature of 7.2ºC and a total rainfall of 3.5mm compared with the Davis’ 7.3ºC and 2.4mm respectively.

Temperature

The big news during April 2021 has been the low temperature, particularly at night. In 2020 the talk was also of temperature, but of heat rather than cold.

Here in East Dorset, April 2021 was colder than March. This has only happened once in the past ten years, in 2012 when once again a cold April followed an exceptionally mild March.

The average number of air frosts at our station in April is TWO between 2010 and 2020. We recorded SIXTEEN air frosts in April, with TEN of those occurring on consecutive nights. This has only been beaten twice in our twelve years of recording, both in the WINTER months: December-January 2009/10 (14) and December 2010 (13). To have this many air frosts in Dorset, in April, is probably unprecedented.

April man temperature

This graph shows the average April temperature over the past ten years. We have also included the 1981-2010 mean April temperature of 8.65ºC, taken from the nearest official weather station at Bournemouth Airport, which we should add is situated within a known frost hollow (as is our own station but to a lesser extent). We should also point out that data from 2012 to 2015 was recorded in Salisbury, Wiltshire, and that from 2016 onwards in Sturminster Marshall near Wimborne, Dorset. However, the difference in official mean April temperature between the two locations is just 0.05ºC.

We have also plotted the trend line in red, which clearly shows a warming trend in spite of the exceptionally cold recent month.

Rainfall

April 2021 was also incredibly dry over large parts of the UK. We recorded just 2.4mm rainfall at WessexWeather, which is only 4.5% of that usually recorded in East Dorset. In fact April 2021 was our station’s 4th driest month since we began recording in 2009., behind April 2011 (0.0mm), June 2018 (0.8mm) and May 2020 (1.8mm).

April rainfall

The above graph plots total April rainfall from 2012-2021 with the average rainfall for East Dorset of 53.9mm. Again the same caveats as above apply. Local comparisons are based on the data from Bournemouth Airport 11 miles away. Aprils in Salisbury (official data from Boscombe Down) are only slightly wetter than those in Wimborne by 2.5mm.

The trend line in red clearly shows that Aprils are becoming drier.

UK-wide

For the UK as a whole April 2021 has been the frostiest April for 60 years with April’s lowest average minimum temperature since 1922. It was also the sunniest on record with an average of 225.1 hours of sunshine (records from 1919); and although very dry in Southern England, for the UK as a whole it was the 4th driest on record.

So what about Spring?

Until we crunched the numbers, we weren’t sure whether Aprils are becoming warmer and drier overall. But clearly they are, and in a relatively short time frame.

So is Spring becoming warmer and drier in the UK? We decided to look at spring as a whole (March-May), which has produced some more interesting results…

Spring mean tempoerature

The graph above shows the mean March-May temperature from 2012 to 2020. Once again a definite warming trend is apparent. It will be interesting to see how Spring 2021 pans out. We will add 2021 at the end of May.

And similarly this spring rainfall graph shows that springs are becoming drier.

EDIT (June 2021): –

The above was written two thirds of the way through a rather dry and cold spring, and specifically one of the driest Aprils on record in the UK. May 2021 by contrast continued the cold theme, but was an extremely wet and windy month with several unseasonably low pressure systems sweeping the UK. It was the wettest May since our records began in 2010, and our wettest month compared with the local 1981-2010 average since at least July 2009.

Spring 2021 was our coldest spring in East Dorset since 2013, but the very wet May was offset by a very dry April, bringing spring 2021 rainfall close to average overall. Spring stats for the UK as a whole: –

  • Frostiest April for 60 years
  • April was colder than March – in fact if not for the last three days in May, the warmest day of Spring 2021 would have occurred on 30th March!
  • Sunniest April on record
  • Wettest May since 1967 in England

Inevitably this has flattened the trend lines shown above: –

Spring mean temperature and rainfall

However, in spite of the unusual spring we have just experienced in the UK, the trend is still the same. Spring is becoming warmer and drier in the UK.

Conclusion

Living from one year to the next it is easy to say that certain months or season are changing. It is only until you see the actual data that one can be sure that this is true. This is one of the reasons we love recording the weather! A stream of random data might not over the longer term be as random as it seems.

So to conclude, is Spring becoming warmer and drier in the UK? Spring in Southern England, in spite of exceptions such as 2013 and 2021, is certainly becoming warmer and drier. This will affect agriculture, water supply and the severity of summer heatwaves given reduced soil moisture.

The climate has been stable for millennia with only minor fluctuations that can take decades or centuries to show. Recent Climate Change is real, and happening over a tiny climatological time frame. Even here at our own station, we have measured tangible changes in only ten years.

If you enjoyed this blog, take a look at some of the projects you can do with your Tempestº weather station, or view the live data here. You can find our longer-term Davis Vantage Vue data on the WessexWeather website. Please comment below, and consider following us on on Twitter and Facebook, and once again thanks for visiting!

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