A large proportion of the piping systems I have viewed recently have ambient temperature as the max thermal condition.
Considering the recent severe climate changes we are experiencing in the UK, it seems 40C is not to far off as an air temperature and looking at Europe's experiences, higher 40's are on the way.
What should now be considered as an acceptable max design temperature to satisfy codes ASME B31.3, BS EN 13480, etc & HSE, bearing in mind anticipated solar radiation heat gain.