being a daily bike commuter for over 4 years now (two years going all 4 seasons) has turned me into an amateur meteorologist because i don't enjoy riding in heavy downpour/thunderstorm conditions (regular rain and drizzle are fine with the right gear). the first thing you learn when you start paying really close attention to the weather is that a forecast of rain tomorrow really only means it's going to be raining at a specific point in time for an unknown duration sometime during the next 24 hours, it doesn't mean that it going to rain solidly for the next 24 hours (at least not here in the american midwest).

getting a good weather radar app for your smart phone is key. i probably look at the weather radar 10 times a day. i'm just obsessed with knowing what's out there, what's on it's way, learning patterns of how systems develop and move through and across my area and how strong or weak they might be. i like tracking systems as they move across the great plains even days before they may get to chicago. i dig deeper into weather forecasts for hourly info to learn what precipitation chances are on an hour by hour basis and figure if the times when i'm gonna be commuting tend to work around those times. and if worse comes to worst, if i ride in the morning and a major storm pops up for the evening ride home i can either just try to wait it out a bit at work (T-storms tend to move pretty damn fast) or if the rain looks unrelenting on the radar, i can as a last resort leave the bike at work and just take the train home and do the same on the way in to work the following morning.

dig deper into the weather in your area. learn more about it. get a radar app. become familiar with the patterns of how systems move through your region. the more you learn about weather, the more you'll be able to stay dry, even on days when the TV weather guy say "well, it looks like rain tomorrow, so grab your umbrellas folks".