scorchingWe're due for another scorching summer day.
swelteringShe won the race despite the sweltering heat.
boilinginformalIt's absolutely boiling in here.
stiflingThe thunderstorm broke the stifling heat of the afternoon.
oppressiveThe oppressive afternoon heat was making him feel tired.
scaldingShe burned herself on scalding water from the kettle.
piping hotusuallyapprovingShe gave us a bowl of piping hot soup.