Overwatering. Happens all the time to butternut. It's their thin skin.
-Mark

Looking at the picture I thought it was a big crack, which would be due to too much water suddenly like Mark said. Which also could mean a sudden rain after a long dry period, not necessarilysomething you did.

Weird. We did get. Big rain last friday, but none of the others split like this. Would this one still be good to eat?

Sure, it's good -- if it's ripe (can't tell from the picture). Of course, the useable squash will be less, since most of it is located in the "handle".

They are good to eat at all times - very young they make good zucchini. Your challenge is to figure out how to cook it, though I am guessing that sauteed with other veggies will work fine.

yep too much all at once, with my pumpkins i look at them careful, and if they are nearing maturity then i watch the weather, but the fruit in your case still very much edible.

len

Here is a link that might be useful: lens garden page

So as they reach maturity are you supposed to cut back on water?