I bike commute year-round, but draw the line at heavy rain, sleet, snow, severe thunderstorms. I just don't like riding in the rain, but will ride on wet roads or during light rain. Cold weather doesn't bother me, and I actually prefer it over high heat and humidity. I would much rather ride on a day with temps are in the 20s than the upper 90s, and I get my fair share of both kinds of days. The hardest part about cold-weather riding is affording all of the gear to make riding comfortable in below-freezing temps, but most cycling gear is well made and will last a long time once you acquire it.