We’re halfway through summer – how cool has it been?

How cool has summer been so far?

We’ve just passed the halfway point of summer, and I’m sure you don’t need me to tell you that it’s been cooler than average so far. But how cool?

The Met Office has just released data for the 1 June to 15 July, which shows that the mean temperature (day and night temperatures combined) has been 1.55C below the average of 13.04C.

How does this compare to past summers at the halfway point? Well, it’s the coolest first half of summer since 2012, which had a mean temperature of 12.77C. Looking further back, it’s the 17th coolest start to summer since 1960.

How wet has it been?

In terms of rainfall, the first half of summer has been very slightly drier than average – driven by June having rainfall 29% below average.

However, the first half of July has been very wet for some, with southern and eastern areas having more than their average for the whole of July in the first two weeks.

Astonishingly, Loftus in North Yorkshire has had 235% of its rainfall for the whole of the month in the first 14 days.

The last very wet first half of summer we had was back in 2012, when the UK had 223.3mm rain – almost double the 113.8mm we’ve seen this year.

South-shifted jet stream

So, why has it been so cool and sometimes unsettled? It’s down to the position of the jet stream, which has been further south and sometimes stronger than average for the time of year.

This has allowed areas of low pressure and cooler air off the Atlantic to dominate our weather – keeping any spells of heat limited in intensity and duration.

For the weather to turn warmer and more settled, the jet stream needs to move further northwards.

What about the rest of summer?

In the next two weeks, there are signs that the jet stream will occasionally move further northwards.

This means that there are likely to be some relatively drier and warmer spells. However, these will probably be focused across England and Wales. Scotland and Northern Ireland may keep the cooler, wetter and windier theme more persistently.

Further into August, the uncertainty becomes too great to offer any sort of clear signal – especially as Atlantic hurricane activity is expected to increase.

A cool anomaly on a warming planet

Despite the UK having a cooler than average start to summer, June was the hottest on record globally – the 13th month in a row to set such a record.

This shows that despite some parts of the world being cooler than average, it’s not enough to offset the clear and notable warming trend that our planet is experiencing due to human-induced climate change.

In the meantime, there’s a brief burst of summer heat on the way for England and Wales to end this week, before cooler and wetter weather returns at the weekend.