So here's a picture of my two little boys rugged up and playing coits. The snow festival in Sapporo has three different event sites and this is the one at a place called TsuDome - which is the giant indoor stadium you can see behind you.
Pretty much all the activities happen outside. Giant ice slides, make your own snowman facilities and this traditional game.
Now the first thing that you'll notice is that it's nice and bright and the snow is white and everything looks fine - in particular if you looked at it on the back of your camera it would look great.
The problem occurs when you look at the histogram (which is why you never want to use your camera's LCD to judge exposure - only the histogram)
Here's a shot of the histogram in camera RAW. The bits that show up in bright red are the bits that are overexposed - beyond 255, no detail whatsoever. And if you look at this photo you'll notice that the entire sky is burnt out. Pure white. In actual fact the detail is there in the RAW file, but I have chosen to sacrifice detail in the sky to have a brighter picture.
If I had decided to keep all the detail in the sky, meaning the rest of the picture would be darker, this is what I would get. As you can see the sky is a pretty ordinary grey with a few wispy clouds. If I follow the rules I now have a picture where everything is within the histogram boundaries and nothing is too overexposed.
But it's a crap photo! So in times like this you need to make a judgement call as to whether you can afford to lose the highlights. Remember that the camera doesn't have the ability to retain as much detail as you can see with your eye. You're limited to only a few f-stops so you have to decide what to lose and what to keep.
Of course if I really wanted to avoid the problem I could just compose the picture so there wasn't any sky in it in the first place - a closeup. Often I do do that to avoid this problem but in this case I wanted to show where the coit toss was happening so chose to keep the sky.
So just remember to keep an eye on that histogram and try as much as possible to avoid having blown-out highlights. But be pragmatic and realise that it's not always possible. Sometimes keeping the highlights will mean the rest of the picture will be too dark. In those cases either crop the highlight parts out by re-composing the picture, or be prepared to lose them.