Manchester United are flying into a Balkans heatwave for the showdown with Real Madrid, with the temperature in Skopje set to hit 40C on Monday.
There will be little respite for Mourinho and Zinedine Zidane’s players at kick-off on Tuesday, with the temperature predicted to remain around 35C.
United and Real played in oppressive heat on their recent pre-season tours of the US, including a game against each other in Santa Clara, but the searing heat in Macedonia’s capital is likely to be the hottest they have endured.
The energy-sapping test in the debilitating against heat comes just five days before Mourinho’s United begin their Premier League campaign against West Ham at Old Trafford.
Health warnings are in place in the parts of Southern Europe where temperatures – the highest recorded for a decade in some regions - have reached potentially dangerous levels.