It’s not a well known climatological fact, but central England temperatures in June have remained little changed in the 361 years since the series started back in 1659. A simple linear trend will reveal that there’s been no more than a 0.003°C warming per decade in all that time. The mean temperatures at the start of the trend in 1659 is 14.28°C, and at the end in 2019 the mean is 14.38°C, a rise of just one tenth (0.1) of a degree in those intervening 360 years.
If you use the more accurate daily mean series which 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 is a fact.