My book once told me something that's proven to be true more often than not:
Rain = Under
Snow = Over
It's equally difficult to play in each but books don't usually adjust the total as much for rain (if at all) the way that they do for snow.
Plus, its been a low scoring affair so far
770/700
You must have some naked pictures of your bookie for him to be so generous with the family secrets.
He's right though, it's tough to adjust for weather on the fly because too large of a swing off the original or current number will result in them being far more exposed to middles and scalps then they would of been if they just left the total alone.