I can hear and see the rain dripping from the box top edge. Whoa, I think that was a lightening flash! Yes, there's the thunder. Sounds like a good bit of wind, and now a real cloud burst.
I see a glimmer of white breast and with another flash, can see Princess is alert, with her wings slightly spread to increase the shelter room underneath. Her front and the chicks under her are out of the rain.
What a miserable night of weather in Winnipeg! Hooray for the nest box and the maternal instinct to protect her young.