Went to post some letters today (short walk) took my Nikon F50 28 mm lens and iSO 25 film, dark clouds I got drenched and 3 pictures took and all within 10 minutes I am back home soaking wet....1/30 F2.8 holds no fear for me, I am expecting blur.
I use my Nikonos V all the time in bad weather. And in good weather if what I am doing may be hazardous to the health of regular cameras.
I shot this with my Nikonos V, the 35mm lens and Fuji Provia 400 two weeks or so ago. As Fstop mentioned, dreary weather is a fantastic time to use colour film. The colour saturation provides contrast and subject isolation that may be lost in a sea of grays in poor weather. Then again, it of course depends on what look you are going for.
Anyway, take the Nikonos! They rock.