As far as I can make out, May 2016 was the 37th warmest in the Central England Temperature [CET] series that started in 1659. It had started coolly but warmed up significantly between the 4th and the 12th when two maximum CET records were broken (8th and 9th), but a colder week followed and wiped out a lot of the positive anomalies that had been gained.
Here are the May rankings since 1659, it certainly was the warmest since the exceptionally warm May of 2008, with a mean anomaly of +1.46°C. So although global temperature records are being broken on a monthly basis, CET records certainly aren’t.
Here is a look at all May’s since 1659.
And finally looking back over the last 62 years of CET monthly anomalies.