Regarding this in the MOD thread:
"July record (36.7c) is 100% going. Decent chance of beating 38.5c and a slight chance of 40c
If pretty much all the models are forecasting 37-38c then you can easily take that as highly likely. Even if you only add a degree you are at 38-39c
If even the pessimistic beeb is forecasting 37c for London, you sit up and take notice. You can usually add 2-3c to their forecast
They are forecasting 35c for my location (Haverhill, Suffolk). That is unheard of. Typically we are around 32c even in 2006, 2013,2015
Once the models are three days out, they are pretty damn reliable and this is a stable situation unlike the plume before. No signs of degradation whatsoever.
Thursday is going to definitely be a record breaker. Perhaps multiple records."
The temperature in London/SE is down by 3-4 degrees (multiple predictions of 26 midday, peaking at 29-30 later) right now with persistent cloud. A lower max today would mean a lower overnight min, which could impact tomorrow's max temp.
So nothing is guaranteed for Thursday despite XYZ predicting record breaking temps.