Gas overflow in winter

[sprtrx300ex]

For some reason, I noticed that more gas has been coming out the overflow tube than normal. It seems to have started when it got colder but I'm not sure. Is there something about colder weather that would make more overflow?

[jb400exxx]

on a 400ex, is it normal for a lot of gas to pour out the overflow when doing wheelies or going up steep hills?