Yep it could have been water!! Another thing I could guess is because it was raining you were looking down slightly so you wouldn't get rain in your eye. So then you tilted the camera up further than normal to compensate you looking down. The camera lens aimed way to high or it's artificial intelligence chose the clouds and couldn't focus because it was just white and most cameras require contrast to focus correctly. Those are the possibilities when you get to know your iPhone. Hah!