On Friday, it’s “Bike to Work” day in D.C., but it may as well be “Wear a Life Jacket to Work” day given the torrents of rain forecast. Biking enthusiasts have complained that it “always” rains on their parade, so I decided to check out this claim.

I examined rainfall amounts on the last 10 day “Bike to Work” days from 2004-2013. With the exception of 2004, when it was held on May 7, Bike to Work day has always occurred on the third Friday of the month.

Of the 10 total days, there has been measurable rain on 5 of the 10 and at least a trace of rain on 7 of the 10.

On average, there are about 12 days with measurable rain during the month of May – or on about 38 percent of the days. So “Bike to Work” day’s 50 percent average is above the norm.

Here’s the actual rainfall data from the past 10 “Bike to Work days:

2013: No rain

2012: No rain

2011: Trace

2010: No rain

2009: 0.15″

2008: 0.53″

2007: Trace

2006: 0.03″

2005: 2.63″

2004: 0.20”

We actually hit a good stretch between 2010 and 2013 with essentially no rain, but it was pretty wet in the years prior.

Unfortunately, the recent run of good luck ends tomorrow (Friday) which has the potential to mimic the deluge of 2005.