- If it is raining, I do not take the bike to work!
- If it is not raining, I take the bike to work.
This method has been serving me pretty well over the years. I've only gotten caught in inclement weather a handful of times.
I used to use more sophisticated means like actually checking the weather forecast. However I found myself missing out on perfectly suitable days for riding. I would check the forecast - It was calling for rain - I would skip the bike - A drop of rain never fell - I felt bad for not riding. I can't count how many times that scenario played itself out.
Last week was a perfect example. The forecast called for winter storm warnings for at least 2 days. Had I heeded these forecast - I would have skipped riding on those days. As it turns out - I was able to ride all 5 days last week. Mind you - it was cold (most days in the 20's) - but it was dry. First of February - I guess I can't ask for anything better than that.