Well for those of us lucky enough to be living in Reading, we can find out how hot (or cold) it is, very accurately, thanks to the University of Reading, and their Meteorlogy Department.
The title link will take you to a site which is not the easiest to understand at first as it is primarily aimed at the scientific community, but give it chance and you might grow to love it.
Of interest to you is the Dry Bulb temperature – the rows of maximum and latest value, are those probably what you are looking for.
It is updated every 5 minutes I think, so count yourselves very lucky, and the weather station has been in operation for a long time so is well respected.
Any questions, I can try to answer, but a lot of it is past my scientific knowledge I’m afraid.
For anyone not in Reading, the Met Office has reasonable data for many weather stations on this link