So far I've canceled a bike commute for two things: Sub-zero temperatures or heavy snow.

Today has neither, but here's the forecast for the afternoon, listed under SEVERE THUNDERSTORM WATCH:
At 2 PM...mostly cloudy with scattered showers and thunderstorms. Some thunderstorms may be severe with damaging winds...large hail...heavy rainfall and frequent lightning. Temperature around 71. Southeast winds 5 to 10 mph. At 4 PM...numerous showers and thunderstorms. Some thunderstorms may be severe with damaging winds...large hail...heavy rainfall and frequent lightning. Temperature around 69. Southeast winds 5 to 10 mph. At 6 PM...numerous showers and thunderstorms. Some thunderstorms may be severe with damaging winds...large hail...heavy rainfall and frequent lightning. Temperature around 65. Southeast winds 5 to 10 mph.


Between the "damaging winds," "large hail," and "frequent lightning," I may have to add this to my list of weather to cancel a commute for.