It's really hot in Madrid right now, close to 35 degrees, so much that Juventus asked UEFA to feature timeouts during tonight's game if the temperature is higher than 32 degrees, according to UEFA.
This would be the first time this rule is used in European football. Remember that it happened a few times during the 2014 FIFA World Cup because of the humidity as well. The weather isn't as humid in Madrid though, so it's surprising to see Juventus requesting this.
The players would be able to drink during the game and the referee would have to add at least 2 or 3 minutes to make up for the time lost, obviously. However, UEFA will likely decline this request, as it has never happened in a Champions League game before and the temperatures aren't that high in Madrid.
How could this affect the game? It would give time for both teams to huddle and discuss tactics too..