This summer was the joint hottest on record in the UK, according to Met Office figures that have heightened concerns about the impact of global warming.

The summer of 2018 will be remembered for a six-week spell from the end of June to the second week of August when daytime temperatures in parts of the country consistently topped 30C (86F).

Although provisional figures have shown that average temperatures this summer just pipped previous record heatwaves, the Met Office said it was too close to declare 2018 as the hottest.

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It said the average summer temperature this year across the UK was 15.80C, marginally above 1976 (15.77C), when there was a widespread drought; 2003 (15.77C), when the highest temperature ever was recorded in the UK; and 2006 (15.78C), when the record for the hottest month was set.

But it said the margin between the mean temperatures of all four years was so small that it was impossible to separate them statistically.

In England the difference was marked enough to officially make it a record-breaking year. Average temperatures were 17.1C, statistically clear of 1976 when the average temperature was 17.0C. The average summer temperatures in other parts of the UK fell below record levels. In Scotland they were 13.6C, below the record set in 2003 of 14.07C. The average in Northern Ireland was 15.1C and in Wales it was 15.9C, both just below record levels set in 1995.

“Having further assessed the temperature data for the UK as a whole for summer 2018 the figures are so close that we are declaring it as the joint hottest on record together with 2006, 2003 and 1976,” the Met Office said in a statement.

“Usually we will only quote statistics to the nearest 0.1C as differences smaller than this could result from small numerical differences arising from the statistical calculations.”

A more comprehensive and definitive analysis of this summer’s temperatures will be conducted in the coming weeks. Many meteorologists believe the recent scorching temperatures will become the new summer norm.

A Met Office spokesman said: “The heatwave and lack of rainfall we experienced in summer 2018 were part of natural cycles in the weather which cause temperatures to be elevated far higher than normal. However the risk of heatwaves is increasing due to greenhouse gas emissions.

He added: “Since the industrial revolution, global temperatures have risen by about 1C, meaning that temperatures experienced in 2018’s heatwave were higher than they would be without the additional effects of global warming.”

Friends of the Earth said the figures were another warning “that we’re racing towards catastrophic climate change”.

Mike Childs, its head of policy, added: “It’s time for the government to take the heat off the planet by ending our fossil fuel fixation, investing in energy efficiency and developing the UK’s huge renewable power potential.”

Tony Juniper, executive director at the environmental campaign WWF, said: “It looks like this will be the new normal, as our rapidly changing climate renders extreme weather ever more likely. We urgently need ambitious action to cut climate-changing pollution and to build a cleaner, greener economy. If we don’t act right away we will pass the point of no return.”