You may have heard that a humid kitchen can adversely affect your pie dough, making it wet and sticky, but it's actually the temperature of your ingredients and equipment that are to blame. Photo by Vicky Wasik.
According to the Patron Saint of Good Baking, Stella Parks, even slightly warm ingredients can soften butter, which is bad news because the texture of your dough depends on keeping that butter cold. She then goes on to drop some serious knowledge on why humidity is not the cause of your pie dough woes:
That's why pie dough seems to need less water on a hot summer day; soft butter functions more like a liquid than a solid in the dough. Folk wisdom says that humidity plays a role in how much water your dough needs, but I've gotta disagree. Flour has a fairly low capacity to absorb moisture from the air, and that very property is what keeps it stable on the shelf. If flour could suck up enough ambient moisture to change how a recipe behaves, it would mould as quickly as a loaf of supermarket bread.
To keep your butter, and resulting dough, nice and chill (21C), you're going to want to pop everything -- wet ingredients, dry ingredients, bowls and rolling pins -- in the fridge until it's all somewhere in between 18-21C. (An instant read thermometer stuck into your flour will let you know when you're there.) You're also going to want to click the link below for more dough tips, including a quick and easy way to cool down a warm counter top.