Although lots of people will remember last year as having very hot temperatures, I've just had a skim of the stats for last year and it doesn't appear to have been that different to this year.
According to a quick google, it didn't start getting warmer until about July 6th. When it was max 23 degrees Celsius and min 14 degrees Celsius. Broken cloud is the description.
NB the results I got were for London
Source: timeanddate.com