Leinster and Ulster will have to deal with an early summer heatwave in northern Spain if they are to win their Champions and Challenge Cup finals.Ulster will play Montpellier at the San Mamés Stadium in the Challenge Cup final in Bilbao at 8pm on Friday, before Leinster take on Bordeaux Bègles at the same stadium in the Champions Cup final at 2.45pm on Saturday.The Spanish state meteorological agency, Aemet, has issued an extreme heat warning for the whole country.Friday afternoon will hit a scorching 38 degrees according to Accuweather, with caution advised for fans travelling to the game if outside for an extended period of time. Temperature is expected to stay close to 30 degrees by the time Ulster’s match kicks off.On Saturday, temperatures are expected to be more than 30 degrees again, with a real feel of 34 degrees around the time of Leinster’s match.It is a jarring change for Bilbao after it had midday temperatures as low as 16 degrees last week. The massive thermal swing has “put health services on alert for heat-related complications” according to Sur in English.Against two teams from the south of France more accustomed to the hot weather, it will be another obstacle for the Irish teams to overcome against stiff French opposition.