I fried fish in my indoor turkey deep fryer last week. It's been outside on my back porch since that day. The temperature outside has been up and down. Although the top has been closed since then. Is it still ok to use it again? 
Generally, it's fine to reuse deep-fry oil. In a lot of restaurants, fryer oil only gets changed when it starts to smoke or make food taste "off". It is not necessary to refrigerate used oil. Assuming it's only used for safe food, oil will taste bad long before it will become unsafe (if it ever really does).  Kenji Lopez-Alt of Serious Eats wrote a great article about reusing fryer oil. In it, he explains how the hydrophobic nature of oil drives moisture out of the food. Assuming the oil reached actual frying temperature (I've never seen a recipe that called for less than 325F/165C), there is no moisture left in those food bits that get left in the oil. Pathogens need moisture to survive and multiply.  For quality sake, ideally, fryer oil should be filtered daily. Leaving bits for days at varied temperatures could negatively affect the flavor, especially since you were frying fish. In the article linked above, Kenji speaks of a technique for cleaning fryer oil using gelatin in much the same way you can use gelatin to clarify stock. I have been meaning to experiment with that, but Kenji is a solidly reliable source so I'll take his word for it. If your fryer oil tastes less than clean, it's worth trying. Fryer oil is expensive!  Relatively harmless oxidation and degradation will eventually cause your oil to not taste good, but it's a common thing to actually add some of the old dirty oil to the new clean oil when cleaning a fryer. Super fresh oil doesn't taste as good as gently used :)  Extremely dirty, stinky oil does produce low levels of certain toxins and possible carcinogens, but not before many uses. As the oil degrades, its smoke point will drop. Smoking oil is not good eats. 