Sally -- 1D III & EF 135mm f2. Click for larger.
Looking through the pictures I took yesterday and I noticed that there are quite a few mis-focused frames when there was heavy snow. Normally, I only use the center focus point for stationary shots and it has been working well for me, but in heavy snow (perhaps heavy rain as well), the focus system gets fooled by the snow. Perhaps, setting the focus system's sensitivity might help, but I have not tried.