Eggs – n upper limit to the “room temperature” at which eggs should be stored

(Unwashed) eggs needn't be stored in a fridge. Well, depends where you live and if the hens get vaccinated against salmonella, that is.

Basically eggs come with a type of natural coating – the cuticle – that protects them from going bad even at room temperature (and seemingly higher) for several weeks (see this question and answers). It's kind of self-evident from the fact that hens will take some time to breed fertilized eggs – at … and usually above room temperature – and it would be odd for the nutrients to go bad while the embryo (chick) needs them to develop.

However, you may have noticed my use of room temperature in the above paragraph. Just like with red wine that's kind of a stretchy term. So since I live in the Northern hemisphere and it's summer time here, I was wondering if there is a rule of thumb of what ambient temperature should not be exceeded for non-refrigerated eggs? (Please cite your sources for the rules you give in your answers!)

NB: Yes, I am aware that by refrigerating eggs early on can considerably prolong the duration until they go bad (even though the eggs are being sold off the shelf; i.e. without refrigeration). But my question is more about trying to find out if there is an upper limit and how the ambient temperature influences the tendency of eggs to spoil. For example if I know that I can easily keep a carton of eggs at up to 30°C for a week, that'd save me quite some space in the fridge when I plan to bake within a week of the grocery shopping.