What makes an egg yolk runny when you crack the egg?

[PixieCutLover]

every once in a while I get a yolk that is not round but just liquid and runs all over, what causes this?

 

[cmom]

I googled what causes runny egg whites and yolks and found this thread. Lately my eggs have had runny whites and not very firm yolks. I have not changed anything. They still get the same feed and extra goodies from the gardens and kitchen as well as oyster shells and grit. It has been exceptionally hot, can the heat be a factor. I have been raising chickens for years but haven't had this problem. Any ideas???

 

[Uzuri]

I've been getting some of this this summer as well and attributed it to the heat, and possibly the age (though they're really not that old) of my hens.