NOAA was telling me 30-50% of precipitation for several hours, and it hasn't rained for a while. I checked weather.com, and it was telling me 10% chance until 8 p.m. for 40%, so I figured what the heck I'm going to leave before it gets worse. Well, I got caught in a thunderstorm. One second there's no rain and the next second bam a massive downpour. There was a bit of flooding and lots of thunder. Much of the time my bike was on the bus rack. It rained so bad that when I got home to wipe it down, there wasn't much black oil left. The cassette looked pretty clean. I'll have to lube it in the morning.