If it reaches the 38c that is predicted for Wednesday and Thursday, then it will be considerably hotter than it reached in 1976, it never reached 38c in the 70s, 80s or 90s.
In fact the first time it ever reached 38c was 10th August 2003. It has reached/exceeded that three times since.
1976 was unusual in that it was sustained heat, over a long period, which affected infrastructure. I was 6 but remember my mum filling the bath with cold water, due to water shortages.
This red warning is not for a heatwave per se, it is because it is unusually high, extreme heat, which has different challenges to 1976, but they do not compare really.