"but away from the ground it hasnt been that hot lately."
Well, on Friday it was! As mentioned in another thread, in Aircrew Notices, I was on BA 0001 on Friday 8th August. The Captain advised us that the external air temp in the FL450 upwards region was 10 degrees C hotter than normal for the time of year. This affected climb and speed. We reached Fl 575 but no higher and M2.0, advised as 1330mph by the flight deck, due to the uncommon heat and the chances of a divert to Gander were very high.