That's how Scots refer to the glorious summer days when the sun hangs out in the sky all day and most of the night. The super long summer days almost make the 3:30 pm sunsets during the middle of winter worth it. Almost; but the thought of all that darkness coming in a few months makes me cringe.
But the long days, oh, they're so fabulous. You never get sleepy; suddenly you realize it's after 11 and it feels like 6. What would make those nights near to perfection is consistently warm weather so you could actually spend time outdoors without wearing a jacket. Oh well, can't have everything.
I took these pictures right around summer solstice at 12:30 am, without a flash. The camera didn't do a great job of recording the true color of the sky; it was actually an even lighter and brighter blue than what it looks like in the photo, but you get the idea. During the longest days, it doesn't ever get completely dark, just hovers around twilight for a few hours until the sun starts coming up again around 2:30. It's pretty amazing.
Come visit us next summer and see it for yourself!