Blackberry winter

Okay kiddo, so "Blackberry winter" is a funny phrase that grown-ups use to describe a sudden cold weather that happens in the springtime.
Imagine if you were playing outside in your shorts and t-shirt, enjoying the warm sunshine, when all of a sudden a cold wind starts blowing and you feel a bit chilly.
That's what blackberry winter is like. It's when the weather gets cold again for a little while, even though it's already supposed to be warm in the spring.
Some people say it's called blackberry winter because it usually happens when blackberry bushes start to bloom. But really, it can happen anytime in the spring.
So if you hear grown-ups talking about blackberry winter, just remember that it's just a funny way to talk about cold weather in the springtime.