Rain is no problem, I commute everyday in the rain (SF Bay Area). I could see it being a bigger issue when I lived in the midwest and had much heavier thunder storms and might not want to be biking but I would usually walk or take the bus. Snow is definitely more of a challenge but much of the danger is due to poor infrastructure, the snowplows pile the snow on the side of the road which removes what was left of the little space bikes have on the road. You can get studded tires for bikes if its icy.