I ride in the rain a lot (grew up and am again living near Seattle). Slow down. Stay in a cage's tire tracks. Consider manhole covers and street striping greased ice. There is NO such thing as rainproof raingear. Take spare clothes, wrapped in gallon ziplock bags,  to change into at work.  The rear brake is pathetic in the dry, beyond useless in the wet. Brake dust + water = a drum full of grease. Make sure you can comfortably use the front brake in any weather conditions.

Rain riding is no big deal. Just allow extra time, and, if the cages are driving beyond stupidly, take to the secondary roads. I refuse to ride the superslab in the dry on my Savage. Maybe when I get my next bike (bigger), I'll try the highway again. But if it's raining, I'll be on surface or frontage roads.
-WD