This has happened to me too. One round I noticed my reticule was much bigger than usual. Can't say for sure but it did feel like the zoom crosshair had become the normal crosshair. Also, the problem was gone on the next round, without mapchange or anything so I don't think the weather had effect.
For what I know, bad weather only effects on crossbow damage and the bolts speed, so that you can't shoot as far as usual and you do less damage.
I've noticed the weather thingy on crpg servers too. When a new map starts it may be very foggy and rainy for everyone, but if you simply rejoin the server you might get nice and clear sky, but still suffer the negative effects of the rain.