It would probably be very hard to see where you are going when flying a broom in the rain, unless you have a hat that had a see-through facial shield. Of course it wouldn't help if the shield got fogged up from breathing to hard.
Nothing that a set of thick aviator googles can't solve. And actually, those would look great on Wilfreda. Thanks, I need to remember that for a... ahem... future story arc.
It's cute little rainy day banter, and it makes sense that if you're going to be slaving over a hot cauldron all day or something then a cool rainy day is the best time to do it. Sweet job on the smiling girls, though Wilfreda's sour expression as she mentions the big exception is super cute too.