Is this all from one device, or are you checking it from different client devices? I recently discovered that the temperature unit setting is stored at the device. So I set HG to F on desktop PC and it worked but on my ipad it would always be incorrect. Then I noticed that the setting was C on the ipad... so it must be stored in cookies? Same goes for the color theme setting.
I should clarify that this is the HG configure-maintenance-ui-temperature unit setting. Not the weather underground setting that I refer to.