I bet that title will come as something of a surprise to a lot of readers, but as far as I can see it’s perfectly true. But before I expand on that, first let’s take a look at June 2019 and see just how it measured up. Basically the cold start to the month was cancelled out by a warm flourish at the end. The mean temperature came in just slightly above average at 14.25°C, which was +0.09°C above the 1961-1990 LTA. There were two record breaking extremes during June, the day maximum of 11.7°C on the 11th was the lowest maximum for that date since 1878, and the day maximum of 30.6°C on the 29th was not only the highest for that date, it was also the highest for any day in June since 1878.
Getting back to that title which hopefully grabbed more people’s attention than if I had put “June 2019 close to average”. If you look at the entire series back to 1659, using a simple linear trend you’ll hopefully find as I did, that there’s been no more than a 0.003°C warming per decade in the last 360 years.
If you use the more accurate daily mean series that started in 1772 you should find that a linear trend shows a slight cooling of -0.003°C per decade. I will admit, from someone who has been interested in the CET series since 1975, that the month of June shows the least warming of any month in the series. Why that is I don’t know but it’s a fact.