You'd probably be surprised. It does certainly take a bigger amount of dedication than I have, but David Beazley's been cycling through Chicago winters (until he cracked a rib earlier this month: https://twitter.com/dabeaz/status/570348015401050112 kept him off for almost a week: https://twitter.com/dabeaz/status/574891782498041857) as for too hot to ride, it's really a matter of good hydration (and physiology, some people can't handle heat at all, but that's cycling or not so they probably know themselves)