question about temperature display in weather apps

Hi all, I have recently begun taking an interest in weather apps, I have tried several accessible ones listed on the website as well as the stock ios weather app. However I have noticed that none seem to offer the option of changing the temperature unit from Fahrenheit to Celsius. I have even hunted through the stock ios app for a setting to do this with no luck. So, can anyone either tell me how to set this in the default ios weather app or recommend me one that provides Celsius as a measure of temperature? Thanks, Alex.