Heat is the enemy of laminated pastry. Professional bakers work in cool environments, but home bakers must adapt. If your kitchen is warm, work in short bursts and refrigerate or freeze the dough between each fold. The butter inside the dough should stay cold and solid - if it becomes soft or melty, it will incorporate into the flour rather than creating separate layers. Some bakers even chill their rolling pins or work on chilled marble slabs. During hot weather, consider making pastry early in the morning when the kitchen is coolest. The goal is to keep butter and dough as separate components until baking, when the butter's moisture creates steam that puffs the layers apart.