GFS did an excellent job of predicting the last heatwave well in advance. Here's it's current thoughts on next Saturday.
The highest temperatures further SW this time. This hot spell may be rather less exceptional, but longer lasting. certainly here in the SW.
What is interesting are the high temperatures over the sea. The effect of the upwelling of deep cold water along the coast of Brittany following an extended easterly wind is clear to see.
Graham
Penzance