I bought a very small jade plant this spring, and after re-potting it I put it on the railing of my balcony when it warmed up (I live in the Puget Sound area). It gets morning sun until about 1:00 - there are no burn marks. And I am careful about not overwatering it. It has more than doubled in size, has lots of new growth, and seemed to be doing really well until now. It has developed not just white spots; rather, some of the leaves are covered completely (on the surface, not the underside) with a white substance that ruins the leaf if I try to scrape it off. (It's probably more likely that it's my fingernail that ruined the leaf when I tried to scrape the white off - only one leaf). I looked up powdery mildew, but none of the images look like my plant.

I'd appreciate your comments. I have high hopes that this plant will grow for years.
PS - for some reason the pics I've posted today are coming out sideways. Not sure how to fix it. Sorry :(

I'm pretty sure the white patches are actually sunburn(!?!) The damage occurred when you put it outside, but didn't really show for a while. I know it sounds crazy but succulents can be like that. The fact that it's only on the top of the leaves and mostly on one side help with the diagnosis. As it's otherwise healthy, enjoy the vagaries of living things' responses to stress and keep doing what you've been doing, your plant looks great.

That's surprising - I always thought burns showed as brown spots - but it sounds right. I've moved it off the balcony railing into the shade of another plant; it still gets bright light, but not direct sun. I guess I'll just cut off the burned leaves.

If it's already been a few days, you could possibly just keep it there. It would be almost hardened off, and used to the direct sun.

Hopefully someone else will chime in and confirm or refute.

Good luck and happy gardening!