I would guess that it's to do with the humidity levels and strength of the wind which both aid cooling. The 'feels like' temperature for Bishop Stortford today has a high of 33c. Compare that with Merryfield for example which had a similar temperature to you today - there 'feels like' had a peak of 42c.
In addition to this (and apologies if I'm wrong) the night time temperature going into last night over EA were lower than other areas in the red warning area and so the cumulative effects less although they were still high.
Originally Posted by: scillydave