St. Patrick’s Day usually conjures images of partying, Catholicism, Irish nationalism and, perhaps most famously, the color green: green clothes, green shamrocks, green beer and green rivers. But the holiday used to be a solemn feast day when you’d be far more likely to see the color blue.

While St. Patrick's Day isn't until Monday, Chicago's iconic tradition dyeing the river green is happening Saturday. Here is how to watch the event.