I live in the Midwest US (specifically southern Wisconsin). Our temperature generally ranges from maybe -10 to +90 F or roughly -20 to +30 C, with occasional weeks that go beyond this range.

I commute to work by bike throughout the year. Admittedly, I avoid the worst of the summer heat by adjusting my work hours so I leave for work before it gets too hot. Also, I'm kind of a freak in the sense that I don't sweat a lot.

If you're curious about this, the weather history feature for Weather Underground will produce nice graphs for most places worldwide.