30% - what's your interpretation?

I don't know if you remember, but way back in June I started the summer with great enthusiasm for commuting by bikng to work. Well, summer didn't - wasn't as cooperative as I had hoped, between my second job schedule, a bout of the flu and the weather, until yesterday I hadn't ridden to work at all. So, as yesterday was the last day of work before the school year officially restarts next week I jumped out of bed at 5am (note the sarcasm) got my gear together and took Mr. Fish and Chips advice and checked the weather report.

"30% chance of scattered showers starting between 1-3pm". Great, I can leave work at 2. But hey only 30% means there is a 70% chance it won't rain right? I've sat at home on days with a higher percent chance and it's been completely dry so I'm not going to let this stop me - plus, scattered showers. It's going to completely miss me, I know it. But somewhere in the back of my head was this little voice reminding me of the 100 mile ride we took a few summers ago with a 40% chance of rain - when it poured for 60% of the ride - that math didn't make sense at all.

So as I left work yesterday afternoon, I could see the big storm clouds up ahead and behind me. I just kept pedaling and thinking about the possible stops if it became torrential. I made it to the half way point, no rain. I pedaled past a possible safe haven shop, no rain. I watched the storm clouds move farther east and begin to clear, still no rain. I felt a drop......... then a few more, but still not a shower. I then found myself in completely soaking wet, puddle filled roads with rain dripping down my glasses and my shoes filling with water. I didn't have much of a choice given my location so I decided to keep going until it became worse. I took my usual route, passed a town line marker and the roads were dry. I made it home a bit soggy but given that the rest of the ride was completely dry and sunny the bike and I dried off before we opened the garage doors.

Yes a long story that doesn't lend excitement to most. The part I like about it is the math. I didn't realize that a 30% chance of rain seems to mean something different in biking terms. It seems the percentage change of rain - refers to that fact that it rained exactly 30% of my ride. I'll keep this in mind next time - but truly I would have ridden if it had been 50% as well - it's only 33 miles each direction after all :)