Spain's players were critical of the playing surface after their 1-1 draw with Italy, saying that it was too dry and slow for them to zip passes about in their usual manner.
"I've already checked the weather forecast and it's going to rain in the morning," the 73-year-old told reporters.
"But that's good because most of my players are from Ireland and play in England so they like the wet."
With striker Robbie Keane chuckling alongside him, Trapattoni added, "Maybe not Robbie. You live in Las Vegas now don't you?"
Earlier in the week Trapattoni said that when he was a player he was used to Spanish sides watering the pitches heavily and he said the Barcelona and Real Madrid players were accustomed to skiddy pitches prepared exactly to their desires.
"I once played a match in Spain, in Coruna, and they watered it so much we were playing in a river."
Spain manager Vicente del Bosque said after the Italy match that a dry pitch "does not do football or the spectators many favours" while Sergio Busquets said he hoped that UEFA would listen to their concerns for the Ireland game.
UEFA said on Tuesday there had been an intention to water the Gdansk pitch more before the Spain v Italy match "but only up to the point where additional watering could cause damage to the surface."
Watering was stopped more than 75 minutes before kick-off on advice from the ground staff.
