Slight rant follows:

So over the past few years of year-round bike commuting in Seattle I've had my fair share of rainy commutes. One thing I've noticed is that waterproof/breathable fabrics aren't. I haven't tried them all but as far as I know they're all basically the same technology with different names. Supposedly, newer ones like eVent are "up to twice as breathable" (as stated on their website) as previous fabrics. If it's not even twice as breathable as most other fabrics, it's not looking too promising. I know that in a laboratory setting these fabrics do allow water vapor to pass through to the outside, but that seems meaningless when you're climbing for 20 minutes with your pit zips open and still overheating and having sweat build up.

About 5 months ago I decided to embrace the rain and just wear the clothes I wear on dry days: poly or wool base layers and a lightweight fleece. The colder and rainy-er, the more layers. I doubt I will ever wear a waterproof/"breathable" jacket again on my commutes. I no longer overheat and the moisture-wicking, warm-when-wet clothes keep me comfortable.

One of these days I'll try an experiment in which I ride at a good clip for an hour or so wearing an old school rubber rain jacket and again wearing a waterproof/"breathable" jacket and compare. Anyone already done something like this?