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Summer 2023 first look

Is record breaking weather likely?

17/04/2023

By Brian Gaze

Will summer 2023 be another record-breaker like last year's? The TWO summer forecast will be issued in late May but before then we will issue two updates taking a look at what the latest data is suggesting. 

Summer sunset in Berkhamsted, Hertfordshire

Seasonal model overview

A range of seasonal models are available. However it is important to remember that their skill level (accuracy) for the UK is low.

The notable things at this stage are:

i) All of the models seem to favour above average temperatures in most of the UK when taken over the 3 month summer period as a whole

ii) As is usually the case the rain signal is less clear. On balance there are suggestions of it being drier than average in the south and wetter than it in the north.

Anomalies masking the outcome

The anomalies in the table may not be telling the complete story. They are for the meteorological summer as a whole and there is a chance that extreme swings are cancelling each other out to an extent. For example, in recent summers there have been several intense bursts of heat despite rather mixed conditions dominating. 

ENSO conditions

The state of the El Niño Southern Oscillation (ENSO) has significant impact on temperature and rainfall patterns around the globe. Nonetheless its link to the UK summer is thought to be weak.

Latest forecasts suggest a 62% chance of El Niño developing during May to July. Analysis suggests that El Niño slightly increases the chance of extreme conditions in UK summers but it isn't generally thought to be one of the dominant drivers of the weather.

Atlantic Hurricane season

Several forecasts for the 2023 hurricane season have been issued. They are suggesting close to or below average levels of activity. 

Colorado State University is predicting 13 named storms of which 6 become hurricanes.

Accuweather is predicting 11 to 15 named storms of which 4 to 8 become hurricanes. 

The predictions suggest the Atlantic hurricane season will not have an anomalous impact the UK summer.

Recent summers

Perhaps the defining characteristic of recent summers in the UK has been the increased frequency of hot spells. Maximum temperatures for recent years:

2022: 40.3C, 19th July, Coningsby, Lincolnshire

2021: 32.2C, 21st July, Heathrow, Middlesex

2020: 37.8C, 31st July, Heathrow, Middlesex

2019: 38.7C, 25th July, Cambridge Botanical Gardens

2018: 35.3C, 26th July, Fathersham, Kent

2017: 34,5C, 21st June, Heathrow, Middlesex

2016, 34.4C, 13th September, Gravesend, Kent (Note: This was in the meteorological autumn)

2015, 36.7, 1st July, Heathrow, Middlesex

Summer 2022 was a record-breaker with 40C being recorded for the first time in the UK. Although 2021 didn't deliver periods of extreme heat, both 2020 and 2019 did.

The last time 30C wasn't reached in the UK was in 1993. In that year the top temperature recorded was 29.7C in East Bergholt, Suffolk. In more recent times, 2007 and 2008 brought 30.1C and 30.2C respectively.

Therefore, recent climatology favours hot spells. There has also been a tendency for months to be above the Central England Temperature (CET) average.  

Summary

1) Seasonal models suggest above average temperatures taken over the June, July and August period as a whole. There is a tentative signal for rainfall amounts to be below the average in the south and above it in the north. 

2) El Niño conditions slightly increase the risk of extreme weather.

3) The latest 2023 Atlantic Hurricane season forecasts are fairly neutral.

4) Recent climatology continues to favour above average temperatures and an increased chance of hot spells.

At this stage a warmer than average summer is favoured. Lower confidence is attached to rainfall levels, but the possibility of it being drier than average in the south and wetter in the north is weakly favoured.

The next update will be issued in mid-May.

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