looks like powdery mildew. Take a look here and see if you can find anything helpful.

Here is a link that might be useful: powdery mildew search

I highly doubt it is powderly mildew. It doesn't budge, even with a fingernail. Also, we are and have been in the middle of a 100 degree + heat wave with no moisture in sight. Thanks though.

My summer squash - crookneck/zucchini cross - has very silvery leaves.

I think it's sunscreen :)

Here is a link that might be useful: Silvery squash leaves

I also doubt it's powdery mildew. But not because "we are and have been in the middle of a 100 degree + heat wave with no moisture in sight.", this because PM is a summertime disease which doesn't require free water on the leaves. Just 98% humidity within the plant canopy.

Also because I don't see any leaf distortion or drying which commonly occurs with PM.

Perhaps it's a wonderful job of normal leaf silvering.

Keep us posted.

I don't think this is powdery mildew. I believe it's called silverleaf disorder and is associated with a white fly.

I think you'll find the second picture on the site looks familiar.
I had the same thing on some eggplants I grew from seed last season. I tossed the worst of them and removed infected leaves from others and they grew out of it. For yours, though, I think you're ok unless the fruit is affected.

Best of Luck!

Susan