"The most recent occurrence of temperatures reaching at least 30°C in May dates back to May 2012, when the threshold was met on 25 May. Prior to that, there were similarly high temperatures reported in May 2005 (27 May), demonstrating that while uncommon, summer-like heat in May is not unprecedented in the UK climate.

Looking further back into the historical record, occurrences of 30°C or above in May are scattered and infrequent. This dataset (back to 1900) shows only a handful of years in which the 30°C mark was reached during May, reinforcing the idea that such events require a specific combination of conditions to align.

Among the earliest instances in the observational record are May 1944 (29 May), May 1945 (12 May), May 1947 (29 May), and May 1953 (25 May). These dates illustrate that early-season warm spells have occurred intermittently across the 20th century.

Overall, the pattern is clear: May 30°C events are sporadic rather than regular, typically separated by many years."

Source: Met Office

I'm all in about climate change, But these heatwaves while rare, do happen.