The weather forecast said there would be rain today. You listened to the forecast, grumbled about it being on a weekend, and planned to do something indoors—maybe not even venture outdoors. 

When you peeked outside the window, the sun was shining and the sky was clear blue. So you stepped outside with an umbrella, just in case, and left your sunglasses at home.

You walked along the lake near where you lived. You had lunch outside. You walked through the park, bumped into a friend, and caught up. The sun stayed out all day. 

As you arrived home, you felt silly for carrying your umbrella all day. You remembered it was supposed to rain. You could’ve easily spent the day indoors. None of this was supposed to happen. 

You’re glad you didn’t trust the forecast, and looked outside the window for yourself. You got your weekend back. 

For how far our collective technology and expertise have come around, forecasting weather still is never a sure thing. Imagine how inaccurate more complicated expert predictions and assumptions are. 
It’s generally useful to maintain a sense of curiosity, and to check for yourself. “Checking the weather” can apply to all sorts of situations.